Monster conversions for Spell & Crossbones

[Quickleaf]

Governor Juan de Ribera
Medium undead (human), lawful evil
AC 15 (heavy armor house rule, padded armor, disadvantage Stealth and swim checks)
HP 104 (16d8+32)
Speed 30 ft
Str 11 (+0) Dex 16 (+3) Con 14 (+2) Int 16 (+3) Wis 20 (+5) Cha 16 (+3)
Saving Throws Intelligence +8, Wisdom +10 (advantage versus turn undead), Charisma +8
Skills arcana +8, deception +8, history +8, insight +10, intimidation +8, investigation +8, nature +8, perception +10, persuasion +8, religion +10
Tools (+5) chess set, forgery kit, mounts (horses), navigator's tools, poisoner's kit, watercraft
Damage Resistances cold, necrotic
Damage Immunities poison; bludgeoning, piercing, and slashing damage from nonmagical weapons
Condition Immunities charmed, frightened, poisoned
Feats magic initiate, magic adept*, resilient, skilled
Senses truesight 120 ft, passive perception 20
Languages English, French, Latin, Spanish, Persian, Portugese
Challenge 16 (XP 15,000); modified Lich and Cleric (war/death) 16

ROLEPLAYING
Bond. Holy Kingdom. Juan de Ribera seeks to create God's "holy kingdom" in Porto Rico, a place free from pirates, heretics, and freeloaders.
Bond. Curse and the Child. As a lich, Juan de Ribera cannot have children, and instead he has stolen Katerina del Corazon's baby girl.
Ideal. Destiny. Nothing and no one can steer Juan de Ribera from his higher calling. (Any)
Flaw. Juan de Ribera's pride knows no bounds, and he is swayed by flattery. He is also obsessed with maintaining the illusion of youth, and responds negatively to anything old and decrepit.
Personality Trait. Juan de Ribera misappropriates bible verses and uses religious proverbs to reinforce his will. He also has a twitch on the left side of his face that manifest when he is angered.

FORTUNES
Code of Honor, Old Salt (mental affliction), Cause (eradication of piracy in the Caribbean), Fencing School (La Destreza), Governor (San Juan)*, Enemy (Brethren of the Coast), Enemy (Katarina del Corazon), Obsession (Fountain of Youth)*, Touched (believes he's been chosen by God to create a "holy kingdom" in the Caribbean)
[SBLOCK=New Fortunes: Governor, Obsession]
Governor: This Good Fortune is unique to NPCs and can only be gained by a PC thru play. A Governor is the primary authority of a colony, and is authorized to administer justice, manage resources, and assign duties to the navy. In fact, a governor has practically unlimited power at their port, restrained only by the realities of rule and the imposition of taxes and rules by their colonial power.

Obsession:You harbor an unhealthy obsession for a specific person, place, or item, and will go to extreme lengths to attain the object of your desire, and tend to see opportunities to attain the object of your desire where the are none.

For example, someone obsessed with the Fountain of Youth will obsessively hoard maps related to finding it, sabotage others who are seeking the Fountain, and suspect unusually well-aged or spry elderly people of knowing secrets about the Fountain.[/SBLOCK]
TRAITS
Flawed Rejuvenation. If Juan de Ribera is killed, he forms a new body by his phylactery in 1d10 days. However, each time he rejuvenates thus, he suffers an affliction of some kind (either mental or physical).
Shroud of Death. Juan de Ribera appears to be a living man in his early 40's. When he casts create undead, any ghouls or wights that he creates retain their living likeness and speech if he so wishes. In addition, when he makes a successful spell attack that has an ongoing effect (such as bane, ray of sickness, hold person, ray of enfeeblement, bestow curse, contagion, geas, or harm), he may also make the target see all creatures as undead for the spell's duration if he wishes.
Spellcasting. Juan de Ribera casts spells as an 16th level cleric with Wisdom as his Spellcasting ability (save DC 18, spell attack +10).
Cantrips message, minor illusion, spare the dying, thaumaturgy, true strike
1st Level (4 slots): bane, command, detect magic, detect poison and disease, dissonant whispers, (domain spells: false life, ray of sickness)
2nd Level (3 slots): detect thoughts, hold person, locate object, zone of truth, (domain spells: ray of enfeeblement, spiritual weapon)
3rd Level (3 slots): bestow curse, clairvoyance, dispel magic, (domain spells: crusader's mantle (necrotic damage), speak with dead)
4th Level (3 slots): banishment, death ward, locate creature, (domain spells: blight, staggering smite)
5th Level (2 slots): contagion, geas, hallow, (domain spells: anti-life shell, cloudkill)
6th Level (1 slot): create undead, harm, word of recall
7th Level (1 slot): symbol
8th Level (1 slot): control weather

ACTIONS
Paralyzing Touch. Melee spell attack. Attack: +10 hit, reach 5-ft, one target. Hit: 10 (3d6) cold damage. The target must make a DC 18 Constitution save or be paralyzed for 1 minute during which it appears to be dead unless closely examined. The target can repeat the save at the end of each of its turns, ending the effect on a success.
Rapier. Melee weapon attack. Attack: +8 hit, reach 5-ft, one target. Hit: 7 (1d8+3) piercing damage, and Juan de Ribera may move 5 feet within the creature's reach or switch places with the creature (his choice).
Command/Destroy Undead (recharge short rest). Juan de Ribera commands all undead of CR 3 or less within 30 feet that can hear and see him, which must make a DC Wisdom save. If the undead is currently controlled by another, it gains advantage on its save. If the undead fails its save, it obeys Juan de Ribera's commands for the next minute or until Juan de Ribera takes offensive action against it. While being commanded, undead cannot take reactions. Alternately, Juan de Ribera can instantly destroy the undead if he chooses.

BONUS ACTIONS
Estocadas. When Juan de Ribera hits a creature with a rapier attack on his turn, he can use his bonus action to deal +2d8 damage.
Touch of Death (recharge short rest). When Juan de Ribera hits with a melee attack, he can use his bonus action to reduce a creature at 37 hit points or less to 0 hit points. Otherwise the creature takes 37 necrotic damage.

LEGENDARY ACTIONS
As a lich, Juan de Ribera can take 3 legendary actions each round, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. Juan de Ribera regains spent legendary actions at the start of his turn. 

Cantrips. Juan de Ribera casts a cantrip he knows.
Rapier. Juan de Ribera makes a Rapier attack.
Spell Defense (Reaction). As his reaction (breaking the normal rules of Legendary Actions), Juan de Ribera can cast a spell as a reaction to being attacked or compelled to make a saving throw. If he is cunning, this may allow him to prevent the attack's effect entirely.
Frightening Gaze (costs 2 actions). Juan de Ribera fixes his gaze on a creature he can see within 10 feet. The target must make a DC 18 wisdom save or become frightened for 1 minute. The frightened target can repeat the save at the end of each of its turns, ending the effect on a success. If the target's save is successful or the effect otherwise ends, the target is immune to Juan de Ribera's gaze for the next 24 hours.

Juan de Ribera was one of the most influential figures in 16th century Spain, serving as Archbishop and Viceroy of Valencia, patriarch of Antioch, preisdent of the Audiencia, and Chancellor of the University of Valencia. Despite his many accomplishments, Ribera was a cold-hearted cleric who despised those who he saw as heretics, traitors, and freebooters, particularly the large Morisco population in Spain, whom he sought on many times to be impressed into slavery, leading to their expulsion from Spain as part of a thinly disguised property grab by King Philip III. Despite this extreme action, Ribera was disgusted by the "weak hand" of the Spanish crown, for he had a far grander vision than any could grasp, a vision of God's kingdom upon earth. In 1611, Juan de Ribera, suffering from a strange malady, imbibed a specifically concocted poison to ease his passing.

What truly became of Ribera was a secret taken to the grave by his most loyal followers. Juan de Ribera bound his soul to a phylactery and was reborn as a lich to continue the pursuit of his grand plan. However, the ritual was flawed and Ribera did not gain the immortality he had hoped for. For many years he visited the ruins of failed attempts to create God's kingdom on earth, undertook pilgrimage to the Holy Land, visited the worst sinners and greatest philosophers. Yet, Ribera needed more time. He became obsessed with finding the Fountain of Youth, which he believed could correct his flawed lichdom and grant him the time he needed to complete his grand plan. All signs pointed to the New World, and under the guise of "Colonel" Juan de Ribera, he navigated his way thru New Spain's politics toward governship of Porto Rico. With a cadre of loyal soldiers and disguised wights, Ribera soon established himself as tyrant of San Juan and an enemy of pirates everywhere.

Despite great wealth, power, and learning gained from over 150 years of life, Ribera found he could never hang on to the elusive things of youth. When he sees signs of aging in his wives, he has them executed or worse, turned in ghouls. He yearns for those things denied to him because of his state of undeath, children of his own most of all. Unable to conceive, he has instead taken to stealing children from those he considers the dregs of society, including Katarina del Corazon's daughter; he raises these children as his own, brainwashing them to see him as a religious leader destined to create God's kingdom in the Caribbean. Ribera even advocates the motion among the Cathoic Church to beatify his "namesake", the lich's pride knowing no bounds.

 

[Quickleaf]

Smiling Jack
Medium aberration (shapechanger), chaotic evil
AC 17 (natural armor)
HP 190 (24d8+72)
Speed 30 ft, swim 40 ft
Str 14 (+2) Dex 16 (+3) Con 16 (+3) Int 16 (+3) Wis 14 (+2) Cha 22 (+6)
Saving Throws Wisdom +7, Charisma +11
Skills arcana +8, deception +11, insight +7, intimidation +11, nature +8, perception +7, performance +11, persuasion +11, stealth +13
Tools (+5) dice, painter's supplies, playing cards, puzzle-boxes
Damage Resistances acid, poison, necrotic, psychic
Damage Immunities cold
Condition Immunities charmed
Feats actor, skilled
Senses darkvision 120-ft (see fine in magical darkness), passive perception 17
Languages speak all languages, telepathy 90-ft
Challenge 13 (XP 10,000); Morkoth Warlock (Great Old One) 15

ROLEPLAYING
Bond. Dagon's Puzzle-Box. Among the many treasures that sunk with La Gloriosa was a puzzle-box which has the power to open gateways to forgotten Abyssal realms; Smiling Jack hopes to recover this puzzle-box in order to free his fellow imprisoned morkoth.
Ideal. Destruction. Like his master, Smiling Jack longs for the primordial days of old, when the land was bare of life and everything lived in the sea, subject to its will. (Evil)
Flaw. Smiling Jack delights in luring victims into a trap from which they cannot escape, whether physically, socially, or morally; even when he has the upper hand, he prefers a convoluted trap to an assured victory.
Personality Trait. Smiling Jack is extremely affable and can find humor in any situation. He also enjoys the latest fashions, no matter how garish, and has a fondness for fine scarves and offbeat art.

FORTUNES
Magic Trinkets (Rod of the Depths*), Secrets of the Deep (overhear telepathic conversations), Beastie Bait (Kraken), Obsession (watching people drown)

ELDRITCH INVOCATIONS
Abyssal Blast*, Agonizing Blast, Devil's Sight, Master of Myriad Forms, Master of the Tides*, Minions of Chaos, Voice of the Chain Master

TRAITS
Actor. Smiling Jack has advantage on Deception and Performance checks to pass himself off as another person, and he can mimic the speech of another person after listening to them for 1 minute.
Amphibious. Smiling Jack can breath both air and water.
Familiar. Smiling Jack has a crab familiar, which he can communicate telepathically with, perceive thru its senses, and speak thru as if it was one of his thrills.
Magic Resistance. Smiling Jack has advantage on his saving throws against spells.
Master of Myriad Forms. Smiling Jack can change his appearance as an action, as per alter self. Maintaining his new appearance does not require concentration. Whatever form he assumes it will always have an obscene creepy smile. His true form is a morkoth, which he reverts to if killed or subjected to moonbeam.
Innate Spellcasting. Smiling Jack casts the following spells (save DC 18, spell attack +11) without material components.
At-will: hypnotic pattern (see below), magic mouth
Once per day: blackwater tide*, glibness, mass suggestion
Rod of the Depths. The rod has 6 charges which it regains at the start of a new day. Smiling Jack can use it to cast control water (6 charges), to induce drowning in a creature (3 charges), to cause ocean water within 300 feet to become to exceptionally clear or murky (2 charges), or cast alter self (aquatic adaptation only) on others by touch (1 charge).
Spellcasting. Smiling Jack casts spells as a 15th level warlock (save DC 18, spell attack +11). He has 3 spell slots of 5th level, and regains his spell slots after a short rest.
Cantrips: eldritch blast, friends, minor illusion, prestidigitation
Level 1 Spells Known: arms of hadar (6d6), dissonant whispers (7d6), find familiar (ritual), tasha's hideous laughter
Level 2 Spells Known: detect thoughts, hold person (4 targets), phantasmal force, suggestion
Level 3 Spells Known: fear, hunger of hadar (2d6/2d6), sending
Level 4 Spells Known: control water (once per long rest), hallucinatory terrain, evard's black tentacles (3d6)
Level 5 Spells Known: conjure elemental (caller from the deeps, once per long rest), dominate person
Thought Shield. Smiling Jack's thoughts cannot be read by telepathy or other means unless he allows it. Additionally, whenever a creature deals psychic damage to him, they take the same amount of damage that Smiling Jack does.

ACTIONS
Multiattack (morkoth form only). Smiling Jack makes a bite attack and 2 claw attacks.
Bite (morkoth form only). Melee weapon attack. Attack: +7 hit, range 5-ft, one target. Hit: 13 (2d10+2) piercing damage, and Smiling Jack may initiate a grapple with a Dexterity (Acrobatics) check. When the creature ends its turn grappled by Smiling Jack it takes this damage again automatically.
Claw (morkoth form only). Melee weapon attack. Attack: +8 hit, range 5-ft, one target. Hit: 6 (1d6+3) piercing damage.
Eldritch Blast. Ranged spell attack. Make three attacks. Attack: +11 hit, range 120-ft, one target. Hit: 10 (1d10+6) damage, and Jack chooses which type: cold, force, necrotic, or psychic. If he deals cold damage, the target's speed is reduced by 10 feet until the start of his next turn. If he deals force damage, the target suffers disadvantage on their Concentration check. If he deals necrotic damage, the target reduces their maximum hit points by the same amount until taking a long rest. If he deals psychic damage, the target cannot take any reactions until the start of his next turn.
Rod of the Depths (costs 3 charges). Smiling Jack points the rod at a creature he can see within 60 feet, and the creature must make a DC 18 Constitution saving throw. On a failed save, water gushes from the creature's mouth and it begin suffocating as if it had just run out of breath; the creature can survive for a number of rounds equal to their Constitution modifier (minimum 1 round). After this time it drops to 0 hit points and is dying. Maintaining this effect requires Smiling Jack's concentration until the target is reduced to 0 hit points.
Create Thrall. Smiling Jack touches an incapacitated humanoid or aquatic beast, and that creature is charmed until remove curse is cast on them or the charmed condition is removed from them. He may have up to 5 charmed thralls. Smiling Jack can communicate telepathically with his thralls, perceive thru their senses, and speak thru them with his own voice so long as they are on the same plane.

BONUS ACTIONS
Aquatic Agility. When underwater in his true form, Smiling Jack can use his bonus action to Dash or Disengage.
Hypnotic Pattern. Smiling Jack can cast hypnotic pattern as an at-will innate spell, though on land the pattern must originate from Smiling Jack. Additionally, he doesn't need to concentrate to maintain it.

LEGENDARY ACTIONS
Smiling Jack can take 3 legendary actions each round, choosing from the options below. Only one legendary action option can be used per turn and only during or after another creature’s turn. Smiling Jack regains spent legendary actions at the start of his turn.

Deadly Lure. Smiling Jack causes any creatures charmed by his hypnotic pattern to move at half their speed (rounded down) toward the pattern, oblivious to hazards en route.
Eldritch Blast. Smiling Jack uses eldritch blast.
Entropic Ward. When a creature attacks Smiling Jack, he can impose disadvantage on the attack. If it misses then Smiling Jack has advantage on his next attack against that creature.
Spell Reflection. When Smiling Jack successfully saves against a spell of 5th level or lower, he can redirect the spell back at its caster (and possibly his or her companions if it was an area effect spell). Spells he reflects function as if cast with a 5th level spell slot  (save DC 18, spell attack +11). If dispel magic is successfully cast upon him, he cannot use Spell Reflection against spells of an equal or lower level to the spell slot used to cast dispel magic for 10 minutes.

Monster Calculations: Smiling Jack
Defense CR 13 = 12 (237.5 effective HP with 25% increase from Damage Resistances) + 1 (20 effective AC with Magic Resistances and Entropic Ward)
Offense CR 13 = 12 (~78.5 damage/round with Entropic Ward) +1 (+11 attack bonus)
Avg CR 13 = (13 + 13) / 2

...backstory will go here...

[SBLOCK=New Spell: Blackwater Tide]
Blackwater Tide
7th-level necromancy
Casting Time: 1 action
Range: 300 feet
Components: V, S, M (bone or scale of a fish that dwells in the deep abyss of the ocean)
Duration: 12 hours

You summon forth the frigid black waters of the Abyss, wherein the rotting corpses of many poor souls fester in the Stygian depths, at a point within range. The blackwater expands at the rate of 100 feet per round in all directions until it covers a half-mile area (2,640 feet). Blackwater acts as magical darkness for creatures underwater, and immersed creatures cannot take bonus actions. 

Any creature entering or starting their turn in the blackwater takes 3d6 cold damage. Any creature ending their turn in the blackwater takes 3d6 necrotic damage and their maximum hit points are reduced by an equal amount until they take a long rest. A creature may make a Constitution saving throw to take only half damage from either of these effects, but if they fail either save, they are weakened for as long as they're in contact with the blackwater and 1 hour thereafter; weakened creatures deal half damage with weapon attacks.

Additionally, creatures in the area of the blackwater - regardless of whether they're on a ship or immersed - must make a Wisdom saving throw or become frightened of it for the spell's duration.

You may end the spell as an action, the blackwater receding at 100 feet per round until it is gone.
[/SBLOCK]

 

[Quickleaf]

Claude du Tourbillon, Enigmatic Financier
Medium humanoid (human), lawful neutral
AC 16 (bracers of defense)
HP 54 (12d8)
Speed 30 ft
Str 9 (-1) Dex 16 (+3) Con 10 (+0) Int 18 (+4) Wis 14 (+2) Cha 14 (+2)
Saving Throws Intelligence +7, Charisma +5
Skills arcana +7, deception +5, history +7, insight +5, investigation +7, mathematics +7, nature +7, perception +5, persuasion +5
Tools (+3) cartographer's tools, navigator's tools
Feats alert, keen mind, mariner*, skilled
Senses passive perception 15
Languages English, Dutch, French, Persian, Spanish, Latin
Challenge 5 (XP 1,800); Wizard (diviner) 12

ROLEPLAYING
Bond. Loved One. His foster son Emanuel Wynn was a buccaneer taken captive by the captain of La Gloriosa before she went down, and du Tourbillon is determined to find him.
Bond. The Grimoire. A book of vast magical power sunk with La Gloriosa, and du Tourbillon wants it, both for himself and to keep it out of the hands of Lè Academie Royale des Sciences and El Ministerio de Intelegencia de Los Indies.
Ideal. A Man is His Word. Failing to honor an agreement or fulfill a promise is the most egregious offense. (Lawful)
Ideal. Free Thinking. Inquiry and curiosity are the pillars of progress. (Chaotic)
Flaw. Most people scream and run when they see a demon or a Maelstrom - du Tourbillon stops to take notes. 
Flaw. No one must ever learn about what du Tourbillon stole from Lè Academie.
Personality Trait. Du Tourbillon is a snob who looks down on those who can't appreciate the finer things in life.
Personality Trait. Du Tourbillon is a stickler for etiquette, ritual, pomp and circumstance.

FORTUNES
Contacts (business associates), Magic Trinkets (Amulet of Proof against Detection, Bracers of Defense), Ship Mage, Trading Company, Black Spot, Enemy (Academie Royale des Sciences), Grog-headed, Obligation (Emanuel Wynn)

TRAITS
Alert. Du Tourbillon can't be surprised while conscious, has a +7 initiative bonus, and other creatures don't gain advantage on attack rolls against him for being hidden.
Amulet of Proof against Detection: While wearing this amulet, du Tourbillon can't be targeted by divination magic and can't be perceived by scrying sensors.
Expert Divination. When du Tourbillon casts a divination spell of 2nd level or higher, he regains one lower level spell slot.
Keen Mind. Du Tourbillon always knows which way is north, the number of hours till next sunrise or sunset, and can accurately recall anything he has seen or heard within the past month.
Merchant. Du Tourbillon is always aware of recent trade route conditions, unusual items passing thru the market, fluctuations in the price and availability of trade goods, and which merchants to avoid or do business with. In addition, he can accurately appraise just about anything given 10 minutes, and when in doubt his Intelligence checks to appraise an item are advantaged. While this won't identify magic items, it will reveal a higher than normal gold piece value and may recall bits of lore about an item that hint at its properties.
Spellcasting. Du Tourbillon casts spells as a 12th level wizard, and his spellcasting ability is Intelligence (save DC 15, spell attack +7). He can prepare 16 spells and usually has the following spells prepared from his spellbook (which has many spells, including all divinations of 1st-5th level).
Cantrips: buoyancy*, light, mariner's boon*, message, mending, ray of frost (3d8)
1st Level (4 slots): detect magic (ritual), fog cloud, shield, unseen servant
2nd Level (3 slots): detect thoughts, locate object, shatter (3d8)
3rd Level (3 slots): clairvoyance, dispel magic, lightning bolt (8d6)
4th Level (3 slots): control water, ice storm (2d8+4d6), locate creature
5th Level (2 slots): cone of cold (8d8), legend lore
6th Level (1 slot): trueseeing
Storm Sense. Du Tourbillon can predict what the weather will be until the next sunrise or sunset. In addition, he also can sense when a storm is supernatural in origin (e.g. summoned by control weather).

ACTIONS
Sword Cane. Melee weapon attack. Hit: +6 hit, reach 5-ft, one target. Damage: 6 (1d6+3) piercing damage.
Ray of Frost. Ranged spell attack. Hit: +7 hit, range 60-ft, one target. Damage: 13 (3d8) cold damage, and the target's speed is reduced by 10 feet until the start of du Tourbillon's next turn.
Third Eye (recharge short rest). Du Tourbillon gains one of the following benefits until he takes a short or long rest, or is incapacitated: darkvision (60-ft), ethereal sight (60-ft), see invisibility (10-ft), or read all languages.

Claude du Tourbillon keeps the truth about himself wrapped under several layers of misdirection, rumor, and bold-faced lies. The reason for his evasiveness is that du Tourbillon once was a member of La Divinacion, that branch of the Academie Royale des Sciences responsible for keeping tabs on enemies of the French mage conspiracy. He gave everything in service to La Divinacion, neglecting his  wife Jenevette and adopted son Emanuel to conduct the Academie's business in the East Indies. During this time du Tourbillon encountered many eastern magical traditions and his horizons expanded so that he began to question the motives of his Academie mentor. He also befriended a Mughal gunner nicknamed Badouin, and the two became developed a close working relationship.

Jenevette, upon stealing secrets of the La Divinacion, would flee with her lover only to be murdered by agents of the Academie. Emanuel would join the navy only to go missing at sea. When du Tourbillon learned of his son's disappearance and that La Divinacion was responsible for Jenevette's death, he shared heated words with his mentor which resulted in a spell duel that left his mentor comatose. While fleeing the reach of the Academie, du Tourbillon's ship was ravaged by the Maelstrom, possibly a parting gift from his former allies, which nearly killed du Tourbillon and left him changed. It was his friend Badouin who pulled him from the wreckage and du Tourbillon's new life began.

Full of remorse, and now wholly against the agenda of the Academie, du Tourbillon adopted his current nome de guer and applied his skills with divination toward building his own wealth. He established a trading company specialized in seeking out wrecked ships and lost treasures, with Badouin as his pursuer and personal aide. All the while he looked for clues of what befell his son Emanuel and what secrets his wife Jenevette was planning to trade which led to her death. Recently, he has tracked his Emanuel to the Caribbean, where his son was a buccaneer and later a pirate. Du Touribllon has organized a party of treasure-hunters to seek the sunken wreck of La Gloriosa which may hold the key to learning his son's fate and dealing a crippling blow to Lè Academie.

 

[Quickleaf]

Seaclaimed Creature (template)

This template is adapted from the excellent 3.5e Seaclaimed Creature template by @Shade. I've tried to do as straight a conversion as possible, changing things only where required by 5e's rules or to avoid redundant random abilities.

Seafaring humanoids who face death's door while on the ocean's are sometimes paid a visit by the legendary pirate Davy Jones. They are offered an opportunity to avoid death, but in return must swear service to Jones and his ship, the Flying Dutchman, for a term of 100 years. Those who accept this fate are changed, becoming more like the creatures of the sea.

"Seaclaimed" is a template that can be added to any humanoid creature. It increases the creature's CR by a total amount equal to the sum of the adjustment value listed by each Seaclaimed Change. Modify the base creature in the following ways:

Speed: A seaclaimed creature gains a swim speed equal to half the base creature's land speed.
Senses: A seaclaimed creature gains darkvision 60-ft.
Amphibious (Trait): A seaclaimed creature can breathe air and water equally well.
Deliver the Black Spot (Action): By making a touch attack against someone who has attempted to escape a bargain with Davy Jones, a seaclaimed creature may place a sickly Black Spot on the target. All sailors who see the Black Spot have their attitude towards that marked one have their attitude shifted one category toward hostile, and Davy Jones and all who serve him receive advantage on opportunity attack rolls against the target (as if they were Marked - see DMG). The Black Spot persists as long as Davy Jones pursues the marked one. A seaclaimed creature may only deliver the black spot on Davy Jones' direct orders.

Seaclaimed Changes: Upon gaining the template, a seaclaimed creature undergoes horrific changes. You can either roll d50 randomly several times to determine a creature's changes. Alternately, if you desire a more structured approach, you can roll/choose changes to increase the creature's CR by a total of +1 (e.g. one +1/2 CR change, one +1/4 CR change, and two +1/8 CR changes), as well as rolling/choosing 2 (1d3) +0 CR changes. For every 10 years of service to the Flying Dutchman, the creature gains a change; thus creatures who've served for many years may have up to 9 changes. The DM may determine these changes randomly or choose them.

Seaclaimed Changes (d50)

+0 CR Changes (d20)

1 - Barnacle Hands (+0 CR): Numerous barnacles grow from the creature's hand, granting it a climb speed equal to the base creature's land speed.

2 - Bioluminescence (+0 CR): Numerous patches of bioluminescent matter dot the seaclaimed creature, giving off light equal to a torch. It can suppress this illumination or restore it once per round as a free action.

3 - Cartilaginous Skeleton (+0 CR): The creature's skeleton becomes soft and pliable, granting it double its proficiency bonus on Strength (Athletics) and Dexterity (Acrobatics) checks to escape a grapple. It also can squeeze without suffering any movement penalty, suffering neither disadvantage to its attacks nor advantage to attacks against it when squeezing.

4 - Chromatic Skin (+0 CR): The seaclaimed creature has the ability to change the color of its skin in complicated and stunning patterns. It can communicate without speech with other seaclaimed creatures that can see these colors (thus darkvision does not work). The creature also gains double its proficiency bonus on Dexterity (Stealth) checks.

5 - Echolocation (+0 CR): The seaclaimed creature's porpoiselike mouth allows it to “see” via echolocation, transmitting sounds inaudible to most creatures, that grant it blindsight 120-ft. A silence spell negates this and forces the seaclaimed creature to rely on its vision.

6 - Flipper Feet (+0 CR): The creature's feet become flippers. Its swim speed improves to its normal base land speed, but its base land speed is then reduced by half (rounded down).

7 - Gummy Secretions (+0 CR): The creature can exude a sticky secretion from its body. Any creature touching it becomes automatically grappled, and checks to escape its grapple are disadvantaged. Likewise, melee weapons stick to it and require a DC 14 Strength check as an action to be freed. Universal solvent will free a creature or weapon from the gummy secretions. Most of the creature's treasure can be found stuck to its body as a form of decoration.

8 - Harpooner's Hooks (+0 CR): Numerous fishing hooks and harpoons are imbedded in the seaclaimed creature who can throw them 30-ft as a ranged attack. A creature hit takes 1d8 + STR piercing damage and must make a (DC 8 + proficiency bonus + Strength modifier) Strength check or be reeled in to a space adjacent to the seaclaimed creature.

9 - Hermit Crab-Head (+0 CR): The creature's head can detach and function separately as a hermit Crab (MM). The creature becomes immune to any attack that requires a creature to possess a head (such as a vorpal sword). Killing its head makes the rest of the body blind.

10 - Kelp-creeper (+0 CR): The seaclaimed creature sprouts protrusions like those of a sea dragon. When in an area of aquatic plant life, it appears completely indistinguishable from the surrounding vegetation.

11 - Manta Wings (+0 CR): The creature grows a pair of powerful pectoral fins like those of a manta ray, which allow it to glide through the water at greater speed. Add +20 feet to the creature's swim speed.

12 - Puffer Fish-Head (+0 CR): The creature's head becomes a puffer fish. When angered or frightened, its head inflates. This grants it Intimidation proficiency (or double its proficiency bonus if already proficiency). Additionally, the creature gains resistance to poison damage.

13 - Sea Snail's Eyestalks (+0 CR): The creatures eyes extend outward on stalks like those of a sea snail, granting it double its proficiency bonus on Wisdom (Perception) checks.

14 - Seaslime (+0 CR): A slimy layer of mucus covers the seaclaimed creature's body, granting it double its proficiency bonus on Strength (Athletics) and Dexterity (Acrobatics) checks to escape a grapple. The sea slime may have other properties, such as being flammable, hallucinogenic if imbibed, and/or corrosive (dealing 1d6 acid damage to creatures coming into contact).

15 - Shellfish Patches (+0 CR): Patches of mussels and similar shelfish grow over the seaclaimed, providing an additional +1 AC (natural armor). It also can blow a conc shell on its body that alerts all seaclaimed creatures within a mile.

16 - Shipwalk (+0 CR): As an action, the creature may meld its body into a ship it is touching and appear out of another ship within 300 ft. The seaclaimed creature must be able to see its destination. The creature's skin takes on the appearance of rotting wood.

17 - Tangling Seaweed (+0 CR): Long strands of kelp and similar plants grow from the seaclaimed creature's body. The seaclaimed can make melee attacks with a reach 5 feet farther than the creature's normal reach and gains advantage on its grapple checks.

18 - Walrus Tusks (+0 CR): A pair of walrus-like tusks grow from the creature's mouth (if it has one), giving it a bite attack that deals 1d8 + STR piercing damage. The creature can also make a loud call alerting all seaclaimed creatures within a quarter mile.

19 - Webbed Digits (+0 CR): The creature's hands and/or feet are webbed, granting it +5 feet swim speed. Give the creature proficiency in Strength (Athletics) checks, or double its proficiency bonus if it is already proficient.

20 - Whiskers (+0 CR): Catfishlike barbels sprout from the seaclaimed creature's face, neck, or shoulders. This grants it blindsight 30 feet in water.

+1/8 CR Changes (d10)

21 (1) - Anchor Arm (+1/8 CR): A boat anchor on a length of chain replaces one of the seaclaimed creature's arms. Treat this arm as a reach 15-ft melee weapon that deals 2d6 + STR bludgeoning damage on a hit. It can never be disarmed.

22 (2) - Angler Fish Jaws (+1/4 CR): The creature's mouth transforms into the oversized jaws of an angler fish, and as its action it may make a bite attack that deals 2d8 + STR piercing damage.

23 (3) - Blubber (+1/8 CR): The natural insulation of the massive amount of blubber on the seaclaimed creature's body gives it immunity to cold. The leathery skin that holds its rolling frame grants +3 AC (natural armor). However, reduce the creature's Dexterity to 10 or less.

24 (4) - Bull Shark's Strength (+1/8 CR): The seaclaimed creature has the strength, testosterone, and vague facial appearance of a bull shark. It gains a Strength score of at least 16 and can make a Shove attempt as a bonus action when it hits on its turn.

25 (5) - Driftwood Head (+1/8 CR): The seaclaimed creature's head takes on the consistency of driftwood, allowing it to add its proficiency bonus on Wisdom saves and making it immune to charm and fear. However, reduces its Intelligence to 8 or less.

26 (6) - Flotsam-dotted Hide (+1/8 CR): Bits of flotsam (such as broken bits of masts, hull, and even captain's wheels) dot the creatures hide, granting it +2 AC (natural armor), but also imposing a -5 feet speed penalty both to its land and swim speeds.

27 (7) - Gut Eel (+1/8 CR): The seaclaimed creature's stomach is an empty hole that has become the nest of a moray eel. Once per round, this eel can strike out at an opponent within 5 feet with a +4 bonus to hit. On a successful attack, it does 1d6 damage with a bite. This eel is supernatural and does not need to eat, sleep, or breathe.

28 (8) - Ink Cloud (+1/8 CR): While submerged, the seaclaimed creature can emit a cloud of jet-black ink in a 10-ft diameter area as a bonus action, then Dash immediately afterward. The cloud provides total concealment, which the creature normally uses to escape a losing fight. All vision within the cloud is obscured. The creature recharges this ability on 5-6 on a d6.

29 (9) - Starfish Attached to Face (+1/8 CR): The creature regenerates 1 hit point at the start of each of its turns that it has more than 0 hit points due to the starfish's blood mingling with its own.

30 (10) - Tentacle-Arm (+1/8 CR): One of the creature's arms is replaced by an octopoid tentacle. It loses any claw or slam attack it possessed with that limb, but can make a tentacle attack with 10-ft reach that deals 1d8 + STR bludgeoning damage and allows them to make a grapple check as a bonus action.

+1/4 CR Changes (d10)

31 (1) - Blood Frenzy (+1/4 CR): The seaclaimed creature gains the trait "Blood Frenzy": The seaclaimed creature has advantage on melee attack rolls against any creature that doesn’t have all its hit points.

32 (2) - Electric Eelflesh (+1/4 CR): The seaclaimed creature can deliver an electrical shock to a single victim within 5 feet. The victim must make a (DC 8 + proficiency bonus + Constitution modifier) Dexterity saving throw or take 2d8 lightning damage.

33 (3) - Fishguts (+1/4 CR): A seaclaimed creature with this change has its innards replaced with dead, rotting fish. It gains the "Stench" trait of the Troglodyte (MM). When hit by an attack dealing piercing or slashing damage, the creature involuntarily releases a spew of foul fishguts. Any adjacent enemies must make a (DC 8 + proficiency bonus + Constitution modifier) Dexterity saving throw or be blinded until the end of their next turn by the guts.

34 (4) - Gulper Mouth (+1/4 CR): The seaclaimed creature grows a distended jaw and a huge, pouchy gullet. It gains the swallow whole special attack and can swallow creatures up to one size category smaller. It may have one swallowed creature at a time. The AC of the seaclaimed creature's gullet is 10. A swallowed creature can try to cut its way free with any light slashing or piercing weapon by dealing damage equal to 10 + the seaclaimed creature's Constitution modifier to the gullet.

35 (5) - Krill Laden (+1/4 CR): The seaclaimed creature's body is full of krill, and as an action it can release a cloud of these tiny crustaceans once per long rest that appears adjacent to the creature. The swarm returns to the seaclaimed creature's body after 1 minute. If destroyed, a new swarm grows within the creature during its next long rest. Treat this as a Swarm of Insects (MM), with the following adjustments: 
Speed: swim 20 ft
Traits: Distraction. Any creature starting or ending its turn in a krill swarm's space suffers disadvantage on Concentration checks.
36 (6) - Lamprey Mouth (+1/4 CR): The creature's mouth twists into the shape of that of a lamprey. As its action the creature may make a bite attack that deals 1d8 + STR/DEX piercing damage. Additionally, on a successful bite attack the creature latches onto its victim as per a grapple. When a victim grappled in this way ends its turn still grappled by the seaclaimed creature, they lose 1d8 + STR/DEX hit points and the seaclaimed creature regains an equal amount of hit points as it drains the victim's blood.

37 (7) - Lobster Carapace (+1/4 CR): The creature gains a lobsterlike carapace, increasing its natural armor by +4 AC

38 (8) - Sea Lure (+1/4 CR): The seaclaimed creature sprouts a glowing, mesmerizing bioluminescent extension that it can use to mesmerize. Any non-seaclaimed creature within 30 feet of the seaclaimed creature must succeed on a (DC 8 + proficiency bonus + Charisma modifier) Wisdom saving throw or be effected by a hypnotic pattern. If the seaclaimed creature attempts to harm the victim, the effect is immediately broken.

39 (9) - Spit Sand (+1/4 CR): The creature can spew wet globs of sand at an opponent within 15 feet. The victim must make a (DC 8 + proficiency bonus + Constitution modifier) Dexterity saving throw, or be blinded until the end of its next turn.

40 (10) - Sponge Flesh (+1/4 CR): The seaclaimed creature's flesh takes on the texture of a sea sponge, granting it resistance to all damage types except for piercing and slashing damage.

+1/2 CR Changes (d10)

41 (1) - Anenome Head (+1/2 CR): The seaclaimed creature's head resembles a brightly-coloured sea anenome, granting it tremorsense 15-ft. The creature can make an extra melee attack with the tendrils on its head, and on a hit deals 1d4 + STR/DEX poison damage, and the victim must make a (DC 8 + proficiency bonus + Constitution modifier) Constitution saving throw or be poisoned for 1 minute. If the seaclaimed creatures hits a victim it has already poisoned, and if that victim fails its save, then they are also paralyzed; at the start of each of their turns, the victim may repeat the Constitution save to shake off the paralysis (but not the poisoning, which lasts the full minute). 

42 (2) - Cold Dead Eyes of a Shark (+1/2 CR): The creature gains a 30-ft gaze attack that inspires fear in living creatures. A victim that fails a (DC 8 + proficiency modifier + Charisma modifier) is frightened of the Seaclaimed creature for 1d4 rounds. A victim that successfully saves is immune to that seaclaimed creature's gaze attack for 24 hours.

43 (3) - Coral Encrustation (+1/2 CR): Half of the creature's body is encased in coral, granting it +5 AC (natural armor) and resistance to piercing and slashing damage. However, reduce its speed by -10 feet, both its land and swim speeds.

44 (4) - Drown (+1/2 CR): The seaclamied creature can make a melee spell attack to try to fill an opponent's lungs with water. A victim touched by the seaclaimed creature loses any air in its lungs and must make a (DC 8 + proficiency bonus + Charisma modifier) Constitution saving throw or begin drowning.

45 (5) - Hammerhead Shark-Head (+1/2 CR): The creature denies enemies from gaining advantage against it due to flanking or numbers (e.g. a rogue would not gain advantage just for having an ally next to the creature). Also, it gains an extra bite attack that deals 2d6 + STR piercing damage.

46 (6) - Jellyfish Tentacles (+1/2 CR): The creature grows a pair of jellyfishlike tentacles somewhere on its neck or torso. When the creature grapples a target, the jellyfish tentacles exude a paralytic secretion. Anyone victim who ends their turn grabbed by the tentacles must make a (DC 8 + proficiency bonus + Constitution modifier) Constitution check or be paralyzed for 6 rounds.

47 (7) - Lobster Claw (+1/2 CR): The seaclaimed creature gains an extra claw attack that deals 2d6 + STR piercing damage. Additionally, on a successful attack with its lobster claw, the creature can initiate a grapple check as a bonus action, and when a creature ends its turn grasped by the lobster claw they take the damage the attack inflicted again automatically.

48 (8) - Siren's Song (+1/2 CR): Every humanoid within 300 feet who hears the seaclaimed creature's song must make a (DC 8 + proficiency bonus + Charisma modifier) Wisdom save, though women have advantage on this save. If a man fails, he is charmed to attempt to reach the seaclaimed creature on his turn by any means. If a woman fails, she is stunned as she is overwhelmed by helpless weeping. A target who succeeds on this save cannot be targeted by the same seaclaimed creature's song for the next 24 hours. See the harpy's "Luring Song" for more details.

49 (9) - Stingray Tail (+1/2 CR): A barbed, whiplike tail grows from the creature ending it a venomous stinger, granting it an extra sting attack  which deals 1d8 + STR/DEX damage. The tail is poisonous, and a victim struck by it must make a (DC 8 + proficiency bonus + Constitution modifier) Constitution saving throw or be poisoned for 1d4 hours. While poisoned they are unable to take bonus actions or reactions for 1d4 hours.

50 (10) - Urchin Spines (+1/2 CR): The creature sprouts spines like those of a sea urchin over its body. Any creature grappling the seaclaimed creature takes 4 (1d8) piercing damage. Also, the creature can fire a spine as a ranged attack up to 80-ft. On a hit it deals 1d8 + STR/DEX piercing damage, and the victim must make a (DC 8 + proficiency bonus + Constitution modifier) Constitution saving throw or become poisoned. If the victim fails its saving throw by 5 or more, it is also paralyzed. At the start of its turn the victim makes this saving throw again to remove the poisoned / paralyzed condition, and if they fail by 5 or more they take 4 (1d8) poison damage. If they succeed, the condition ends and they are immune to that particular seaclaimed creature's poison for 24 hours.

 

[Quickleaf]

"Blackheart" Garcí del Corazón
Medium undead (human, seaclaimed), neutral
AC 19 (unarmored defense, natural armor, dual wielder)
HP 150 (16d8+64)
Speed 20 ft, swim 10 ft
Str 18 (+4) Dex 16 (+3) Con 18 (+4) Int 9 (-1) Wis 15 (+2) Cha 16 (+3)
Saving Throws Dexterity +8, Constitution +6, Wisdom +6, Charisma +7
Skills athletics +8, acrobatics +7, insight +6, intimidation +7, perception +6, performance +7, stealth +11
Tools (+4) cartographer's tools, navigator's tools, watercraft, bandore, lute, mandolin
Damage Immunities cold, poison, pressure
Condition Immunities frightened, poisoned
Feats Dual Wielder, Resilient, Skulker, Tough
Senses darkvision 60-ft (no perception disadvantage in dim light), passive perception 16
Languages English, Aquan, French, Spanish, Thieves' Cant, telepathy 60-ft (with seaclaimed creatures only)
Challenge 10 (XP 5,900); Seaclaimed* Pirate* (swashbuckler*) 12, Bard 1

ROLEPLAYING
Bond. Sworn to the Abyss.
Ideal. Redemption. Blackheart loathes the deal he made with Davy Jones, and longs for a way to regain his humanity or truly die.
Flaw. Blackheart is supremely patronizing, particularly to those younger than him. He also has overpowering greed.
Personality Traits. Blackheart is prone to making predictions of doom with tongue-in-cheek humor. He is adorned in numerous fetishes, drogues, and religious symbols. His language is as foul as an otyugh nest.

FORTUNES
Notoriety, Seaclaimed*, Magic Trinkets (Dry-fire Pistol* & Battleaxe +2 combined as a pistol-axe attachment replacing his missing hand), Magic Trinkets (Instrument of the Bards: fochlucan bandore with variant spell list & Horn of Valhalla: silver as a conc shell), Magic Trinkets (Cloak of Elvenkind & Scimitar of Wounding), Magic Trinkets (many drogues*), Accursed, Affliction (missing hand & peg leg), Obsessed with Treasure, Obligation (Davy Jones)

SEACLAIMED CHANGES
chromatic skin, shellfish patches (natural armor), shipwalk, ink cloud, cold dead eyes of a shark, siren's song

SEAFARER TRICKS
dead reckoning, favored ship (Heart of the Sea), issue commands, night raid, pirate's curse, sea legs, storm sense

TRAITS
Amphibious. Blackheart can breathe air and water equally well.
Blackheart's Cloak. When his hood is up, Blackheart has advantage on Dexterity (Stealth) checks, and observers have disadvantage on Wisdom (Perception) checks to see him thanks to the cloak's camouflage. Pulling the hood up or down requires an action.
Cursed. Blackheart is cursed with the Black Spot, and his touch is deadly to those he loves. Also, if Blackheart is reduced to 0 hit points, so long as his body is returned to the sea he will be return to life 24 hours later by Davy Jones and gains an Obligation ill fortune.
Dead Reckoning. Under a clear sky, whether night or day, Blackheart always know the direction of true north, can precisely intuit distances with his naked eye, and cannot get lost at sea. When traveling at fast pace aboard a ship he does not suffer the -5 penalty to  passive Wisdom (Perception). Also, when using a spyglass he has advantage on Wisdom (Perception) checks to identify ship features.
Drogues. Blackheart has numerous protective charms. At dawn he gains advantage on his saving throws against one specific type of threat (e.g. siren charm); this lasts until dawn the next day when he can change what specific threat his charms protect against.
Favored Ship (Heart of the Sea). While aboard Heart of the Sea, Blackheart has advantage on any checks to pilot the ship, move about the ship, search the ship, stowaway aboard the ship, or recall information about its design.
Sea Legs. When fighting aboard a ship, when Blackheart rolls initiative he may Dash or Use an Object for free so long as he isn't  surprised. Also, he ignores difficult terrain due to sea state, and disadvantage from sea state to Dexterity (Acrobatics) or Strength (Athletics) checks.
Skulker. Blackheart can hide when only lightly obscured. If he misses with a ranged attack while hidden he doesn't reveal his position.
Spellcasting. Blackheart casts spells as a 1st level bard, and his Spellcasting ability is Charisma (save DC 15, spell attack +7).
Cantrips: booming captain's voice*, drowned likeness*
1st Level (2 slots): bane, detect magic (ritual), disguise self (as mortal version of self only), thunderwave (2d8)
Storm Sense. Blackheart can predict what the weather will be until the next sunrise or sunset. In addition, he also can sense when a storm is supernatural in origin (e.g. summoned by control weather).
Swashbuckling Step. On the first turn of combat, when Blackheart acts before other creatures, his movement does not provoke opportunity attacks from creatures he acts before. Also, when Blackheart successfully Overruns, Tumbles past, or Pushes Aside a creature, he does not provoke opportunity attacks from that creature.
Wounded Fury. While he has 30 hit points or fewer, Blackheart has advantage on all attack rolls, and he deals an extra 9 (2d8) damage to any target he hits with a melee attack.

ACTIONS
Multiattack. Blackheart makes 3 attacks, one of which may be ranged.
Pistol-Axe (axe). Melee weapon attack. Attack: +10 hit, reach 5-ft, one target. Hit: 10 (1d8+6) slashing damage. If Blackheart hits when he has advantage on his attack, he may attempt to Shove the target as part of the attack.
Pistol-Axe (pistol). Ranged weapon attack. Attack: +7 hit, range 30-ft/90-ft, one target, loading. Hit: 8 (1d10+3) piercing damage.
Cutlass of Wounding. Melee weapon attack. Attack: +8 hit, reach 5-ft, one target. Hit: 7 (1d6+4) slashing damage. Once per turn, when Blackheart hits a creature with his cutlass, he can wound the target. At the start of each ofnthe target's turns it suffers 1d4 necrotic damage per wound it has received. It gets a DC 15 Constitution save after this to end the effect of all wounds upon it; alternately, the wounded creature or an adjacent creature can make a DC 15 Wisdom (Medicine) check as an action to end the effect of such wounds.
Conc Shell (once per week). Blackheart summons 7 (2d4+2) Seaclaimed Berserkers from the sea, which appear within 60 feet of him. They return to the sea after 1 hour or when they drop to 0 hit points.
Deliver the Black Spot. Blackheart attempts to touch a living creature who has attemptd to escape a bargain with Davy Jones; the creature must make a DC 15 Reflex save or be afflicted with a sickly Black Spot. All sailors who see the Black Spot have their attitude towards that marked one have their attitude shifted one category toward hostile, and Davy Jones and all who serve him receive advantage on opportunity attack rolls against the target (as if they were Marked - see DMG). The Black Spot persists as long as Davy Jones pursues the marked one.
Fochlucan Bandore. Blackheart can cast the following spells (save DC 15, spell attack +7) using his bandore. Each of the following spells may be cast once per day: beast sense (aquatic only), entangle, faerie fire, fog cloud, gaseous form (self only), levitate (sunken creatures/objects only), spare the dying, speak with animals (aquatic only).
Pirate's Curse (recharge long rest). Blackheart may cast bestow curse (save DC 15) on a creature that has grievously wronged him. This version of bestow curse doesn't require somatic components or touch; instead it requires that the creature be within 30 feet, can hear Blackheart, be capable of speech (though it need not speak the same language), and have dealt him grievous wrong.
Shipwalk. While aboard a ship he captains, Blackheart can teleport anywhere within the ship. Also, he can teleport from one ship to another he can see within 300 feet. He teleports by stepping into a sail or shadow, and emerging from a sail or shadow on the other ship.
Song of Longing. Every humanoid within 300 feet who hears the song must make a DC 15 Wisdom save. If they fail, they are charmed to attempt to reach Blackheart on their turn by any means. If they fail by more than 5, they are stunned and overwhelmed by helpless weeping until the start of Blackheart's next turn. A target who succeeds on this save cannot be targeted by Blackheart's song for the next 24 hours. See the harpy's "Luring Song" for further details.

BONUS ACTION
Cold Dead Eyes of a Shark: Blackheart makes a gaze attack against living creatures within 30 feet. A victim that fails a DC 15 Wisdom save is frightened of Blackheart for 1d4 rounds. A victim that successfully saves is immune to Blackheart's gaze attack for 24 hours.
Cunning Action. Blackheart takes the Dash, Disengage, Hide, or Overrun action.
Cutlass Attack. When Blackheart uses an action to attack, he can make a cutlass attack as a bonus action.
Issue Commands. Blackheart issue commands to all friendly creatures within 60 feet who can hear and understand him. Until the start of Blackheart's next turn, those creatures gain advantage on one of the following of Blackheart's choice: ability checks involving nautical tasks, melee attacks, or ranged attacks (a creature with multiple attacks gains this benefit on the first attack it makes only).

REACTION
Ink Cloud (recharge 5-6). While submerged, Blackheart can emit a cloud of jet-black ink in a 10-ft diameter area as his reaction to being attacked, then Dash immediately afterward. The cloud provides total concealment. All vision within the cloud is obscured.
Reactive Commands. When any number of friendly creatures within 60 feet must make a saving throw, Blackheart can issue commands granting advantage on their saving throws. The creatures must be able to hear and understand Blackheart.
Underhanded Tactics. When a creature misses Blackheart with an attack they had disadvantage on, Blackheart may Shove them as his reaction.

Monster Calculations: Blackheart
Defense CR = 11.5 = 8 (187.5 effective HP with 25% Cold Dead Eyes of a Shark (frightful presence) modifier) + 2.5 (21 effective AC with Cunning Action used half the time) +1 (Ink Cloud & Spellcasting bane and gaseous form)
Offense CR = 8 = 6 (~40 damage/round with Wounded Fury for one round) +2 (+12 effective attack bonus with Cunning Action used half the time)
Avg CR = 11.5 + 8 / 2 = 9.75

 

[Quickleaf]

Seaclaimed Berserker
Medium humanoid (human, seaclaimed), neutral evil
AC 13 (natural armor)
HP 72 (9d8+27)
Speed 30 ft, climb 30 ft, swim 15 ft
Str 18 (+4) Dex 12 (+1) Con 17 (+3) Int 9 (-1) Wis 11 (+0) Cha 9 (-1)
Skills stealth +5
Damage Immunities cold, pressure
Senses darkvision 60 ft, passive perception 10
Languages English, Aquan, Spanish
Challenge 3 (XP 700)

SEACLAIMED CHANGES
barnacle hands, blood frenzy, bull shark's strength, flotsam-dotted hide, harpooner's hooks, hammer-head sharkhead / lobster claw / stingray tail

TRAITS
Blood Frenzy. The seaclaimed berserker has advantage on melee attack rolls against any creature that doesn’t have all its hit points.
Shove. When the seaclaimed berserker hits with a melee attach, it may attempt a Shove as part of that attack.
Wounded Fury. While it has 15 hit points or fewer, the seaclaimed berserker deals an extra 7 (2d6) damage to any target it hits with a melee attack.

ACTIONS
Multiattack. The seaclaimed berserker makes two attacks from those available to it. Each berserker has either Hammer-head Bite, Lobster Claw, or Stingray Tail.
Boarding Axe. Melee weapon attack. Attack: +6 hit, reach 5-ft, one target. Hit: 8 (1d8+4) slashing damage.
Harpoon. Ranged weapon attack. Attack: +6 hit, range 30-ft, one target. Hit: 7 (1d6+4) piercing damage, and the target must make a DC 13 Strength saving throw or be pulled into a space adjacent to the seaclaimed berserker.
Hammerhead Bite. Melee weapon attack. Attack: +6 hit, reach 5-ft, one target. Hit: 11 (2d6+4) piercing damage. The berserker ignores any disadvantage it would have on its attack roll when making this bite attack.
Lobster Claw. Melee weapon attack. Attack: +6 hit, reach 5-ft, one target. Hit: 11 (2d6+4) piercing damage, and the berserker can initiate a Grapple as a bonus action. When a creature ends its turn grasped by the lobster claw they take the damage the attack inflicted again automatically.
Stingray Tail. Melee weapon attack. Attack: +6 hit, reach 5-ft, one target. Hit: 7 (1d8+4) piercing damage, and the target must make a DC 14 Constiuttion saving throw or be poisoned for 1d4 hours. While poisoned they are unable to take bonus actions or reactions.

Monster Calculations: Seaclaimed Berserker
Defense CR 1 = 1 (hit points) 
Offense CR 5 = 3 (~21 damage with Wounded Fury for one round) +2 (+10 effective attack with Blood Frenzy)
Avg CR 3 = (1 + 5) / 2