Death Butterfly Swarm

Family: Insects Rodents & Vermin

Large swarm of Tiny beasts, unaligned

Armor Class 15 (natural armor)
Hit Points 60 (11d10)
Speed 5 ft., fly 40 ft. (hover)

1 (-5) 14 (+2) 10 (+0) 1 (-5) 12 (+1) 12 (+1)

Damage Vulnerabilities cold, fire
Damage Resistances bludgeoning, piercing, slashing
Condition Immunities charmed, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned
Senses darkvision 60 ft., passive Perception 11
Challenge 4 (1,100 XP)
Proficiency Bonus +2


  • Potent Poison. Undead with resistance or immunity to poison damage or the poisoned condition can be affected by the swarm’s poison.
  • Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny insect. The swarm can’t regain hp or gain temporary hp.
  • Weight of Wings. A creature that starts its turn in the swarm’s space has its speed halved and must succeed on a DC 12 Dexterity saving throw or become blinded. Both effects end when the creature ends its turn outside the swarm’s space. On a successful saving throw, the creature is immune to the blinding effect of Weight of Wings for the next 24 hours.


  • Bites. Melee Weapon Attack: +4 to hit, reach 0 ft., one creature in the swarm’s space. Hit: 21 (6d6) piercing damage, or 10 (3d6) piercing damage if the swarm has half of its hp or fewer. The target must make a DC 12 Constitution saving throw. On a failure, it takes 10 (3d6) poison damage and is poisoned until the end of its next turn. On a success, it takes half the damage and isn’t poisoned.


Enormous clouds of orange and green butterflies add a reek of putrefaction to the air, stirred by the flapping of delicate wings.

Demon-Haunted. A death butterfly swarm results when a rare breed of carrion-eating butterfly, drawn en masse to the stench of decay, feeds on the corpse of a fiend, demon, or similar creature.

Dizzying and Poisonous. The colorful, chaotic flapping of the insects’ wings blinds and staggers those in its path, allowing the swarm to necrotize flesh from those it overruns. Attracted to rotting material, the swarm spreads a fast-acting, poison on its victims, creating carrion it can feed on immediately.

Devour the Undead. Undead creatures are not immune to a death butterfly swarm’s poison. A swarm can rot an undead creature’s animating energies as easily as those of the living.

Given the choice between an undead and living creature, a death butterfly swarm always attacks the undead, finding ghouls and vampires particularly appealing. Some good-aligned forces regard summoning these swarms as a necessary evil.

Section 15: Copyright Notice

Tome of Beasts 1 ©2023 Open Design LLC; Authors: Daniel Kahn, Jeff Lee, and Mike Welham.

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