D&D 5E (2014) Help Me Create an Epic Final Boss Fight!

[jayoungr]

Hi, folks! A two-year campaign is coming to a close in a couple of days, and I could use some help making the final fight extra special.

The party is level 8 (bard, warlock, fighter, barbarian, rogue, and a custom class shaman). They will be fighting their way through a mist-infested abandoned village to face down the evil spirit that has cursed the place. The spirit is bound to a cracked clay vessel and cannot move (much) from its place, but its influence covers the whole territory. Their object will be to weaken the spirit enough to force it back into the vessel and then use mending to repair the vessel.

More useful information about the setup:

• The evil spirit's powers have been established as follows:
  • Mist causes illness (but this should be fairly slow-acting)
  • Voices from the mist can lure the unwary
  • The mist is full of hostile shapes, either spawned by or part of the boss (no one is quite sure which)
• The party includes a glamour bard who has no offensive spells but is our primary healer. The bard likes to spam mantle of inspiration for temporary hitpoints and free movement, plus is also the only character in the party to have calm emotions.
• The warlock has a necklace of fireballs that she's itching to use.
• I have a custom map which is quite large, so it should take the party a few rounds to reach the boss.
  • Thinking of having low-level enemies spawn every round to slow the party down and soak up some of those fireball charges.
• Legendary actions and lair actions are desirable.
• The party has an artifact, a bell that makes evil spirits cower before it when rung. I'm thinking something like a turn undead effect on lesser spirits (that only lasts one round so they have to keep ringing the bell continuously), and maybe imposing disadvantage on the boss.

Help me figure out how to make this an epic fight!

I'm thinking of a lair action requiring a wisdom save to avoid being charmed by voices from the mist. Maybe another one with a save to avoid illness, but I'm not sure how to represent failure; the poisoned condition would be too strong in this case. Waves of enemies should probably spawn each round, but how many and what level? I could reskin something as a mistwraith, but I'm also not sure what base monster to start with.
Any suggestions??

 

[Storyteller Hero]

The animated corpses of the original villagers

Mirrors on the walls that the spirit can use to teleport between locations

NOTE: Does the party have a plan to make sure the spirit is not able to simply run away? One easy idea is that the spirit is afraid of sunlight because they were originally a killer executed in daylight by being swarmed with ants while tied to a pole, fearing the dawn since that was when the ants came out of their burrows.

 

[Ulorian - Agent of Chaos]

• The warlock has a necklace of fireballs that she's itching to use.

It would be cool to slip in a horde of mooks that could be wiped with a fireball. If this group was a later round introduction, I could see the warlock dropping a fireball on this crowd making for a memorable moment. Even if accompanied by a heftier individual or two; the mooks get incinerated, the leaders are still there, but suitably weakened and demoralised, their surprise attack thwarted... good stuff.

But of course, if they show up, and aren't whittled down by the fireball(s), your fight scene gets increased in difficulty tremendously. But that's part of the fun honestly...

 

[jayoungr]

NOTE: Does the party have a plan to make sure the spirit is not able to simply run away?

Yes, they have information about the spirit's past and how it was bound to the vessel.

 

[J-H]

Where did the spirit come from? What are its themes beyond spooky and causes disease and fog?
I know you want a boss fight, but this sounds more like undifferentiated manifestations of its presence rather than a single boss.

Here's a Poison Mist elemental. It can be nearly invisible in the fog, so it makes a good surprise attacker, and it seems like it's on-theme as something they encounter.

Spoiler: Poison Mist CR 7

Poison Mist
A grey-green form swirls in the mist, reaching forwards with two insubstantial arms. A brown cloud seems to swirl around it, obscuring its precise position.
Medium Elemental
Armor Class 14
Hit Points 90
Speed 30’ fly
Str Dex Con Int Wis Cha
6(-1) 18(+4) 16(+3) 6(-2) 14(+2) 8(-1)
Skills Stealth +7
Resistances acid, cold, necrotic
Damage Immunities Non-magical weapon damage, Poison
Vulnerabilities thunder
Condition Immunities Charmed, Exhaustion, Grappled, Frightened, Paralyzed, Poisoned, Prone, Restrained, Unconscious
Senses Blindsense 60’, passive Perception 12
CR 7
Blur Attack rolls against the Poison Mist suffer disadvantage, unless the attacker has a way to sense invisible enemies.
Poison Aura Any living creature who starts its turn within 10’ of the Poison Mist takes 2d12 poison damage and is Poisoned for one round. A DC 14 Constitution save halves the damage and negates the Poisoned condition.
Actions
Multiattack. The Poison Mist attacks twice, using any of its melee or ranged attack options.
Dissolving Touch. Melee Weapon Attack, +7 to hit, 5’, 2d6 acid damage. On a successful hit, the next attack against the target has advantage.
Gaseous Swipe. Melee Weapon Attack, +7 to hit, 5’, 3d6 poison damage.
Poison Bubble. A target within 30’ must make a DC 14 Constitution save or take 2d12 poison damage.

 

[Rabulias]

Maybe failing the saving throw against the poison gives disadvantage on Wisdom saving throws?
And failing a Wisdom saving throw makes one see illusionary opponents (or friends?) within the mist that lead the PCs away from the boss, or maybe they entice the PCs into breaking the clay vessel.

 

[jayoungr]

Where did the spirit come from? What are its themes beyond spooky and causes disease and fog?

It's prehistorically ancient. Here is the lore the players have about it in game. (Pardon my Korean.)

An-gae and Eo-duun

Two evil spirits roamed the land, causing much terror and distress. They were known as An-gae, the mist, and Eo-duun, the darkness. These two spirits were allies and delighted in using their powers together: for the one would drive people out of a settlement and into a trap laid by the other.

An-gae brought a cold mist that shut out the sun. Strange, monstrous shapes roamed the mists of An-gae, and voices called from within, attempting to lure the unwary. Those who entered were stricken with sickness, led astray to their doom, or torn apart by the strange creatures within. Some say the mist creatures were An-gae's minions, while others believe they were part of An-gae himself.

Eo-duun brought fire and shadow, patches of darkness that no light could illuminate, and strange grasping limbs like those of an octopus. The sound of Eo-duun's laughter could drive to insanity all those who heard it. Those whose bodies survived Eo-duun's attacks might lose their minds, becoming mere vessels of his will.

But in the end, for reasons no one knows, they had a falling-out. An-gae visited the shaman Pyo Ji and told her how to capture Eo-duun. Pyo Ji led a group of shamans who managed to seal Eo-duun within a clay vessel. But she did not trust An-gae, believing that the spirit only wanted to hunt the land alone. So when Eo-duun offered to help capture An-gae in turn, Pyo Ji agreed to the plan.

Eo-duun told Pyo Ji to bring him to the place now known as Gohyang, and to let him out of his vessel so that he might call An-gae to that place. Pyo Ji did so, leaving five shamans to guard Eo-duun's vessel so that he could not escape, for as long as it was intact he could not move from the place. When An-gae came in response to Eo-duun's taunting, there was a great battle and An-gae was captured. But there was as much gain as loss, for during the confusion, Eo-duun managed to dominate the mind of one of his guards, so that the guard smashed the clay vessel and allowed Eo-duun to escape.

Pyo Ji established a shrine at Gohyang, where the vessel containing An-gae might be guarded so that the spirit could never escape. She devoted the rest of her life to hunting for Eo-duun. Finally, in her old age, having heard that Eo-duun had been seen in the northern mountains, she led a group of nine shamans there to capture him again; but none ever returned from that journey.

An-gae is the spirit they will be fighting. (Eo-duun goes on to become the warlock's patron.)

Also: I just remembered something very important I left out of the original post, which I have now edited in. The party is in possession of an artifact that makes evil spirits cower before it. The whole rest of the campaign was about reassembling the pieces of this artifact. I'm thinking something like a turn undead effect on lesser spirits, and maybe imposing disadvantage on the boss.

 

[Koloth]

The spirit is bound to the clay vessel. What happens if the clay vessel is destroyed? Spirit unbound and free? Or destroyed? What happens if the clay vessel is mended with the spirit on the outside? Which character has the mending spell? Does the spirit know this? If so, spirit could direct summoned allies to target said character(s). No mending spell, no binding, victory spirit. Forcing the party to defend a specific character could raise the stakes. Possible same scenario if the vessel is destroyed? Could be some irony if the spirit could free itself by summoning something to destroy the vessel but doesn't know this.

If the only things the spirit can summon are undead that can be effected by the artifact, it greatly diminishes the power of the spirit. On the other hand, if the spirit can summon something(s) that can detect the artifact and attack the character carrying the artifact, could force the party to defend that character. Or maybe the spirit could summon something that could steal the artifact from the character. Why should pickpocket only be something the PCs get to do? Picture the PCs chasing the mob of little monkeys, one of which is carrying the stolen artifact. Does the party risk a fireball to kill the monkeys with a risk the artifact fails a save?

 

[J-H]

Thanks for the additional info. Here are two more ideas:
Mist Casters
On initiative count 20, the mist spawns 2-3 enemies within 60' of the party (fog visibility may make them invisible, but audible, so they can be targeted with disadvantage). The enemies are made of mist, and have around 30 hit points. On initiative count 5, the enemies move 30' towards the party, and cast a spell if they can get within range of a target. Their spell list is limited to:
Mind Sliver
Crown of Madness
Enemies Abound
Confusion
Contagion

Most of these spells require Concentration. The mistforms will be easy to kill, but someone is going to fail a save about once a turn.

Aura of Hunger
I also once did a ghoul lord (used him in my 14th level Trail of the Hungering Dead as a boss) who had a 30' Aura of Hunger. Living creatures who start their turns within 30' of him must succeed on a Charisma saving throw. On a failure, they must make a melee attack against the nearest living creature, moving up to their speed to do so. Perhaps villagers tore each other apart instead of encountering strange creatures?

 

[Moving Pictures]

Aura of weakness - toss out a level of exhaustion on a failed save.
Given what you've got going on, I like the idea of the BBEG splitting into three portions - recombining into a more powerful singular being.