5E: Monstrous Arthropods for Fifth Edition

[Cleon]

Odonatid, Giant (Diminutive Giant Dragonfly)
Small beast, unaligned
Armor Class 14
Hit Points 7 (2d6)
Speed 10 ft., fly 50 ft. (hover)

STR​	DEX​	CON​	INT​	WIS​	CHA​
7 (–2)​	18 (+4)​	10 (+0)​	1 (–5)​	12 (+1)​	5 (–2)​

Saving Throws DEX +6
Skills Perception +3
Senses passive Perception 13
Languages —
Challenge 1/2 (100 XP) Proficiency Bonus +2

Evasive Flight. A giant odonatid gains advantage on Dexterity saving throws when flying and attackers have disadvantage on attack rolls against it.
 If the giant odonatid is mounted or grappling an opponent, it must make a DC 12 STR check to use Evasive Flight each time it is attacked.

Expert Aerialist. The giant odonatid has advantage on Dexterity (Acrobatics) checks when flying.

Flyby. The giant odonatid doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Keen Sight. The giant odonatid has advantage on Wisdom (Perception) checks that rely on sight.

Motion Camouflage. If the giant odonatid moves at least 20 feet towards a creature and then hits it with an attack on the same turn, that target must make a Wisdom (Perception) check against a Dexterity (Acrobatics) check by the odonatid. On a failure, the target cannot use Dodging Flight, Evasive Flight, or a similar defensive ability to avoid attacks by the giant odonatid until the start of its next turn.

Actions

Multiattack. The giant odonatid makes two attacks against a Tiny or smaller creature. The first attack is a legs attack. If this succeeds in grappling the target, the odonatid makes a bite attack, otherwise it makes a second legs attack.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 3 (1d6) slashing damage.

Legs. Melee Weapon Attack: +6 to hit, reach 5 ft., one Small or smaller creature. Hit: The creature is grappled (escape DC 8). Until this grapple ends, the target is restrained, and the giant odonatid can't make legs attacks against another target.

Bonus Actions

Dashing Flight. The giant odonatid flies up to 50 feet. It cannot use Burst of Speed if it used Dodging Flight after the start of its previous turn.

Reactions

Dodging Flight. If a creature of at least Tiny size attempts a melee attack against a giant odonatid, or the odonatid is targeted by a ranged weapon of similar size such as a giant-hurled boulder, the insect can try to dodge out of the way as a reaction. The giant odonatid makes a Dexterity saving throw with advantage (it loses this advantage when mounted or grappling an opponent). If the saving throw beats the attack roll or DC of the attack the giant odonatid takes no damage and flies up to 20 feet.
 If a giant odonatid is carrying or grappling a creature that is too heavy for the odonatid to fly with, it must release the creature to use Dodging Flight. If the odonatid is grappling a creature light enough to carry through the air, the grappled creature can make an escape check as a free action. If it fails, the odonatid may fly away with its victim.


Description

This dragonfly is maybe 3 feet long and 15 pounds, with a 4 to 4½ foot wingspan. Its habits are the same as its bigger relatives (see Giant Dragonfly for details). It is not big enough to view most humanoids as prey, but might attack children, halflings, or other Small humanoids.

VARIANT: DIMINUTIVE GIANT DAMSELFLY
While still being a Small beast, some varieties of giant damselfly are even shorter and lighter than an average giant damselfly (see Giant Damselfly for details). A diminutive giant damselfly averages 4 to 4½ feet in length, with a wingspan of 4 to 6 feet. It has a diminutive giant dragonfly's statistics except for being slower (fly 40 ft., Dashing Flight 20 ft., Dodging Flight 20 ft.). Diminutive giant damselfly naiads are similar in size to diminutive giant dragonfly nymphs.

VARIANT: DIMINUTIVE GIANT TENEBROUS & UNDERDARK HELICOPTER DAMSELFLIES
The majority of monstrous helicopter damselflies can see in the dark far better than any natural damselfly, with tenebrous species that hunt in the gloom of forests and nighttime and even subterranean varieties native to the underdark (see Mammoth Helicopter Damselfly for details, under Tenebrous Helicopter Damselflies and Underdark Helicopter Damselflies). A diminutive giant damselfly of these variants uses a diminutive giant dragonfly's statistics except for having better senses—the tenebrous variety has blindsight 10 ft., darkvision 40 ft.; the underdark variety, dubbed a lesser ghostwing, has blindsight 30 ft., darkvision 60 ft.

(Monster designed by Casimir Liber and Cleon on Enworld.org's General Monster Talk Creature Catalog Forum; inspired by the giant dragonfly that debuted in EX2 The Land Beyond the Magic Mirror (1983) by Gary Gygax.)

 

[Cleon]

Odonatid, Giant (Diminutive Giant Dragonfly Nymph)
Small beast, unaligned
Armor Class 14 (natural armor)
Hit Points 10 (3d6)
Speed 30 ft., swim 10 ft.

STR​	DEX​	CON​	INT​	WIS​	CHA​
8 (–1)​	14 (+2)​	11 (+0)​	1 (–5)​	12 (+1)​	5 (–2)​

Skills Stealth +6
Senses blindsight 10 ft., passive Perception 11
Languages —
Challenge 1/4 (50 XP) Proficiency Bonus +2

Ambusher. In the first round of a combat, the giant odonatid has advantage on attack rolls against any creature it surprised.

Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d8) slashing damage and the target is grappled (escape DC 9). Until this grapple ends, the target is restrained, and the giant odonatid can't bite another target.

Death Mask (Recharge 4–6). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d8) piercing damage. If the target is a Medium or smaller creature, the target is grappled (escape DC 9) and must make a DC 9 Strength saving throw. On a failure, the target is knocked prone, and the giant odonatid can drag the target closer and make one bite attack against it as a bonus action. Until this grapple ends, the odonatid cannot use its Death Mask attack again.

Jet Dash (Recharge 5–6). The dragonfly nymph swims up to 60 feet.


Description

Apart from being a couple of feet long, this dragonfly nymph is no different from the larger giant odonatid nymphs (see Giant Dragonfly Nymph for details). They are ferocious enough to consider attacking humanoids considerably larger than them. Many nymphs of this size are not actually larvae of diminutive giant dragonflies, but young instars of bigger giant dragonflies. Even the titanic tropical dragonfly has nymphs that hatch out far smaller than this (see Giant Dragonfly for Giant Odonatid Sizes & Variants).

VARIANT: DIMINUTIVE GIANT DAMSELFLY NAIAD
This is the larva of a Small giant damselfly of less than average size (see Diminutive Giant Dragonfly for details). A diminutive giant damselfly naiad is about 3 feet in length and uses a diminutive giant nymph's statistics, except it is faster (30 ft., swim 30 ft.) and loses the nymph's Jet Dash action option.

VARIANT: DIMINUTIVE GIANT TENEBROUS & UNDERDARK DAMSELFLY NAIADS
These are larvae of monstrous damselflies adapted to live in dark environments (see Mammoth Helicopter Damselfly for details, under Tenebrous Helicopter Damselflies and Underdark Helicopter Damselflies). A diminutive tenebrous damselfly naiad has blindsight 10 ft. and darkvision 40 ft.

A diminutive underdark damselfly naiad uses a diminutive giant dragonfly nymph's statistics, except it moves as well on land as water (30 ft., climb 30 ft., swim 30 ft.), has blindsight 30 ft. and darkvision 60 ft., and gains the following additional trait.
 Amphibious. The underdark damselfly naiad can breathe air and water.

VARIANT: DIMINUTIVE GIANT TERRESTRIAL DAMSELFLY & DRAGONFLY LARVAE
This is a diminutive giant damselfly naiad or diminutive giant dragonfly nymph adapted to live on land, although It cannot survive dry conditions for long (see Giant Dragonfly Nymph for details, under Terrestrial Giant Odonatid Larvae). A diminutive terrestrial odonatid larva uses a diminutive giant dragonfly nymph's statistics, except it moves better on land than water (30 ft., climb 20 ft., swim 10 ft.), loses the Jet Dash action option if it's a dragonfly nymph, and gains the following additional trait.
 Limited Amphibiousness. The terrestrial odonatid larva can breathe air and water, but it needs to be drenched in water at least once every 4 hours to avoid suffocating.

(Monster designed by Casimir Liber and Cleon on Enworld.org's General Monster Talk Creature Catalog Forum; inspired by the giant dragonfly nymph that debuted in EX2 The Land Beyond the Magic Mirror (1983) by Gary Gygax.)

 

[Cleon]

Odonatid, Giant (Dainty Giant Damselfly)
Tiny beast, unaligned
Armor Class 13
Hit Points 3 (2d4 – 2)
Speed 10 ft., fly 30 ft. (hover)

STR​	DEX​	CON​	INT​	WIS​	CHA​
3 (–4)​	16 (+3)​	8 (–1)​	1 (–5)​	12 (+1)​	5 (–2)​

Saving Throws DEX +6
Skills Perception +3
Senses passive Perception 13
Languages —
Challenge 1/8 (25 XP)  Proficiency Bonus +2

Evasive Flight. A giant odonatid gains advantage on Dexterity saving throws when flying and attackers have disadvantage on attack rolls against it.
 If the giant odonatid is mounted or grappling an opponent, it must make a DC 12 STR check to use Evasive Flight each time it is attacked.

Expert Aerialist. The giant odonatid has advantage on Dexterity (Acrobatics) checks when flying.

Flyby. The giant odonatid doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Keen Sight. The giant odonatid has advantage on Wisdom (Perception) checks that rely on sight.

Motion Camouflage. If the giant odonatid moves at least 20 feet towards a creature and then hits it with an attack on the same turn, that target must make a Wisdom (Perception) check against a Dexterity (Acrobatics) check by the odonatid. On a failure, the target cannot use Dodging Flight, Evasive Flight, or a similar defensive ability to avoid attacks by the giant odonatid until the start of its next turn.

Actions

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 1 slashing damage.

Legs. Melee Weapon Attack: +5 to hit, reach 5 ft., one Tiny or smaller creature. Hit: The creature is grappled (escape DC 6). Until this grapple ends, the target is restrained, and the giant odonatid can't make legs attacks against another target.

Bonus Actions

Dashing Flight. The giant odonatid flies up to 20 feet. It cannot use Burst of Speed if it used Dodging Flight after the start of its previous turn.

Reactions

Dodging Flight. If a creature of at least Tiny size attempts a melee attack against a giant odonatid, or the odonatid is targeted by a ranged weapon of similar size such as a giant-hurled boulder, the insect can try to dodge out of the way as a reaction. The giant odonatid makes a Dexterity saving throw with advantage (it loses this advantage when mounted or grappling an opponent). If the saving throw beats the attack roll or DC of the attack the giant odonatid takes no damage and flies up to 10 feet.
 If a giant odonatid is carrying or grappling a creature that is too heavy for the odonatid to fly with, it must release the creature to use Dodging Flight. If the odonatid is grappling a creature light enough to carry through the air, the grappled creature can make an escape check as a free action. If it fails, the odonatid may fly away with its victim.


Description

The smallest of giant odonatids, a dainty giant damselfly has a slender body about 18 inches long, an 18–30 inch wingspan and weighs 8 ounces. Its appearance and habits are the same as the regular Small sized giant damselflies (see Giant Damselfly).
 While they are considerably larger and heavier than any normal damselfly or dragonfly, a dainty giant damsel is similar in size and shape to the biggest examples of the odonatids prehistoric griffinfly ancestors, such as Meganeura monyi or Meganeuropsis permiana, and their statistics can be used for these Meganisoptera. Tiny giant odonatids are too small to pose any real threat to humanoids unless they attack in unnatural swarms (see Swarm of Giant Damselflies for details).

VARIANT: SMALL GIANT DRAGONFLY
Some varieties of giant dragonfly are far smaller and lighter than even a diminutive giant damselfly (see Giant Dragonfly for Giant Odonatid Sizes & Variants). A dainty giant dragonfly is 12 inches long, with an 18 to 24 inch wingspan. It has a dainty giant damselfly's statistics except for being faster (fly 40 ft., Dashing Flight 40 ft., Dodging Flight 20 ft.).

VARIANT: DAINTY GIANT TENEBROUS & UNDERDARK HELICOPTER DAMSELFLIES
The majority of monstrous helicopter damselflies can see in the dark far better than any natural damselfly, with tenebrous species that hunt in the gloom of forests and nighttime and even subterranean varieties native to the underdark (see Mammoth Helicopter Damselfly for details, under Tenebrous Helicopter Damselflies and Underdark Helicopter Damselflies). A dainty giant damselfly of these variants uses a dainty giant damselfly's statistics except for having better senses—the tenebrous variety has blindsight 10 ft., darkvision 30 ft.; the underdark variety, dubbed a lesser ghostwing, has blindsight 20 ft., darkvision 40 ft.

(Monster designed by Casimir Liber and Cleon on Enworld.org's General Monster Talk Creature Catalog Forum; inspired by the giant dragonfly that debuted in EX2 The Land Beyond the Magic Mirror (1983) by Gary Gygax.)

 

[Cleon]

Odonatid, Giant (Dainty Giant Damselfly Naiad)
Tiny beast, unaligned
Armor Class 13 (natural armor)
Hit Points 5 (2d4)
Speed 20 ft., swim 20 ft.

STR​	DEX​	CON​	INT​	WIS​	CHA​
5 (–3)​	14 (+2)​	10 (+0)​	1 (–5)​	12 (+1)​	5 (–2)​

Skills Stealth +6
Senses blindsight 10 ft., passive Perception 11
Languages —
Challenge 0 (10 XP) Proficiency Bonus +2

Ambusher. In the first round of a combat, the giant odonatid has advantage on attack rolls against any creature it surprised.

Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 2 (1d4) slashing damage and the target is grappled (escape DC 7). Until this grapple ends, the target is restrained, and the giant odonatid can't bite another target.

Death Mask (Recharge 4–6). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 2 (1d4) piercing damage. If the target is a Small or smaller creature, the target is grappled (escape DC 7) and must make a DC 7 Strength saving throw. On a failure, the target is knocked prone, and the giant odonatid can drag the target closer and make one bite attack against it as a bonus action. Until this grapple ends, the odonatid cannot use its Death Mask attack again.


Description

A miniature version of the standard giant damselfly naiad about a foot in length (see Giant Damselfly Naiad for details). While it is far larger than any normal odonatid larva it poses no real threat to a humanoid, although it might give a nasty nip if mishandled. Like diminutive giant odonatid larvae, many dainty giant naiads are early instars of more formidable odonatids such as the giant damselfly, giant tropical damselfly, imperial tropical damselfly or even the mammoth tropical damselfly (see Giant Dragonfly for Giant Odonatid Sizes & Variants).

VARIANT: DAINTY GIANT DRAGONFLY NYMPH
This is the larva of a Tiny giant dragonfly (see Dainty Giant Damselfly for details). A dainty dragonfly nymph is usually 5 to 9 inches long and uses a diminutive giant damselfly naiad's statistics, except it is slower (30 ft., swim 10 ft.) and gains the following action option.
 Jet Dash (Recharge 5–6). The dragonfly nymph swims up to 40 feet.

VARIANT: DAINTY GIANT TENEBROUS & UNDERDARK DAMSELFLY NAIADS
These are larvae of monstrous damselflies adapted to live in dark environments (see Mammoth Helicopter Damselfly for details, under Tenebrous Helicopter Damselflies and Underdark Helicopter Damselflies). A dainty tenebrous damselfly naiad has blindsight 10 ft. and darkvision 30 ft.

A dainty underdark damselfly naiad uses a dainty giant damselfly naiad's statistics, except it moves as well on land as water (20 ft., climb 20 ft., swim 20 ft.), has blindsight 20 ft. and darkvision 40 ft., and gains the following additional trait.
 Amphibious. The underdark damselfly naiad can breathe air and water.

VARIANT: DAINTY GIANT TERRESTRIAL DAMSELFLY & DRAGONFLY LARVAE
This is a dainty giant damselfly naiad or dainty giant dragonfly nymph adapted to live on land, although It cannot survive dry conditions for long (see Giant Dragonfly Nymph for details, under Terrestrial Giant Odonatid Larvae). A dainty terrestrial odonatid larva uses a dainty giant damselfly naiad's statistics, except it moves better on land than water (20 ft., climb 15 ft., swim 10 ft.), loses the Jet Dash action option if it's a dragonfly nymph, and gains the following additional trait.
 Limited Amphibiousness. The terrestrial odonatid larva can breathe air and water, but it needs to be drenched in water at least once every 4 hours to avoid suffocating.

(Monster designed by Casimir Liber and Cleon on Enworld.org's General Monster Talk Creature Catalog Forum; inspired by the giant dragonfly nymph that debuted in EX2 The Land Beyond the Magic Mirror (1983) by Gary Gygax.)

 

[Cleon]

Okay, I've updated the Want List of Monstrous Arthropods and the Index of 5E Monster Arthropods with the above.

That might be it for today, unless I actually finish the Underdark Helicopter description.

Which seems unlikely, as I keep on getting distracted.

 

[Casimir Liber]

I'm avoiding statting them up proactively as I seem to always get something wrong - so just making verbal suggestions for these when you take the lead

 

[Cleon]

I'm avoiding statting them up proactively as I seem to always get something wrong - so just making verbal suggestions for these when you take the lead

As you like.

If you see any iffy numbers or dodgy grammar in the work so far, please feel free to point it out.

 

[Casimir Liber]

absolutely!

 

[Cleon]

Finished the Mammoth Helicopter Damselfly with the following addition to its Description:

UNDERDARK HELICOPTER DAMSELFLIES
Deep beneath the earth is the Underdark, a mysterious maze of tunnels, crevices and caves. The greatest of its caverns are unbelievably vast and teem with life in forests of weird fungi and strange subterranean seas. In this sunless realm, the ecosystem is powered by dissolved chemicals, geothermal warmth, and the Underdark's own eldritch radiations.
 Some of these sunless seas and mushroom jungles swarm with shimmers of giant damselflies who explorers from the surface have dubbed Ghostwings from their eerie appearance. A ghostwing is two or three yards long, with body and legs that look so thin they're almost translucent, and to normal eyes it is colored pallid white with spots of deathly grey. However, it is actually strikingly patterned in garish hues that are only visible to darkvision—many of these darkvision colors don't even have names in Common. Despite their spooky appearance, ghostwings are relatively harmless, and mostly only attack normal bats and spiders, Tiny giant flies, and creatures of similar size. A ghostwing damselfly is a Small or Medium underdark helicopter damselfly (see Giant Damselfly or Giant Dragonfly for statistics).
 That is far from the case for the mammoth underdark damselfly, a rare monster that can reach lengths of 50 feet or more. They have many names, such as Death Phantom or Web Killer and are hated and feared by the Underdark's inhabitants, especially the drow,. Mammoth underdark helicopters show a great fondness for eating subterranean giant spiders and the drow themselves, so the dark elves go to great lengths in attempts to eradicate them, with little success. A death phantom damselfly is a Huge underdark helicopter damselfly (see Mammoth Helicopter Damselfly or Titanic Tropical Dragonfly for statistics).
 The main reason the drow have failed to exterminate the Huge underdark damselfly is ghostwings and death phantoms are actually one extraordinarily tenacious species. The drow are unaware of this, and would be unable to destroy every ghostwing in the Underdark even if they knew. The larvae of underdark helicopter damselflies are able to metamorphose into adulthood from a range of instars (larval growth stages) far wider than any natural odonatid, with adult sizes ranging from a Small ghostwing to a Huge death phantom. The adults then mate and females lay their eggs in water to hatch into the next generation of naiads, which become adults themselves when environmental cues trigger their transformations. In general, naiads who share their water with larger predators transform into adulthood as early as possible, becoming ghostwings and flying off to somewhere safer , explaining why they are so common. However, if a naiad is very successful, it becomes one of these "larger predators" itself before it is old enough to metamorphose, in which case it attempts to reach Huge size and become a death phantom.
 Underdark helicopter damselfly naiads can become intermediary adults between a ghostwing and death phantom in size, but this is unusual. This typically only happens when their water pool is just big enough for a single naiad to develop into a Large underdark helicopter damselfly, a creature dubbed a Wraithwing by the surface dweller who discovered it (see Imperial Giant Dragonfly for statistics).
  An underdark damselfly's eggs can survive out of water for an impressive length of time, lying dry and dormant until conditions are better. In addition, underdark damselfly naiads are incredibly adaptable, able to live in an incredible range of water temperature and chemistry, from near-boiling brine to crystal-clear icewater, and also are amphibious, able to breathe air as well as water. While they prefer to live in water, an underdark damselfly naiad only has to be submerged when it hatches from its egg, or when a naiad of Large size or bigger needs to molt its exoskeleton and grow into its next instar (see Mammoth Helicopter Damselfly Naiad for details).
​

That satisfies me enough I'm going to do another update:

Updating the Giant Damselfly.
Updating the Giant Dragonfly.
Updating the Imperial Giant Dragonfly.
Updating the Mammoth Helicopter Damselfly.

 

[Cleon]

So I think the basic adult giant damselflies and dragonflies are about done.

I'll leave the wee little ones (Dainty & Diminutive) and the jumbo sized (Titanic) ones to simmer on the back burner for the mo. They oughtn't to take long, as they're just stronger and weaker variations of the existing odonatids. It's basically just a question of changing some numbers.

Time to turn my attention to the Nymphs and Naiads…