The Prince of Swarms

Large fiend (devil), lawful evil

Armor Class 17 (natural armor)
Hit Points 275 (22d10 + 154)
Speed 40 ft., burrow 20 ft., climb 40 ft., fly 80 ft. (hover)

22 (+6) 20 (+5) 25 (+7) 19 (+4) 21 (+5) 25 (+7)

Saving Throws Dex +12, Con +14, Wis +12, Cha +14
Skills Deception +14, Insight +12, Perception +12, Stealth +12
Damage Resistances acid, cold; bludgeoning, piercing, and slashing from nonmagical weapons that aren’t silvered
Damage Immunities fire, poison
Condition Immunities charmed, frightened, poisoned, stunned
Senses truesight 120 ft., passive Perception 22
Languages Celestial, Common, Draconic, Infernal, telepathy 120 ft.
Challenge 21 (33,000 XP)

Special Traits

  • Legendary Resistance (3/Day). If the Prince of Swarms fails a saving throw, it can choose to succeed instead.
  • Magic Resistance. The Prince of Swarms has advantage on saving throws against spells and other magical effects.
  • Magic Weapons. The Prince of Swarms’s weapon attacks are magical.
  • Innate Spellcasting. The Prince of Swarms’s spellcasting ability is Charisma (spell save DC 22, +14 to hit with spell attacks). The Prince of Swarms can innately cast the following spells, requiring no material components:
  • Fear Aura. Any creature hostile to the Prince of Swarms that starts its turn within 20 feet of it must make a DC 22 Wisdom saving throw, unless the Prince of Swarms is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature’s saving throw is successful, the creature is immune to the Prince of Swarms’s Fear Aura for the next 24 hours.
  • Aura of Virulence. Creatures that would normally be resistant or immune to poison damage or the poisoned condition lose their resistance or immunity while within 120 feet of the Prince of Swarms. All other creatures within 120 feet of the Prince of Swarms have disadvantage on saving throws against effects that cause poison damage or the poisoned condition.
  • Swarm Prince. The Prince of Swarms can communicate with his spawn and all vermin and insects, including swarms and giant varieties, within 120 feet via pheromone transmission. In a hive, this range extends to cover the entire hive. This is a silent and instantaneous mode of communication that only the Prince of Swarms, his spawn, insects, and vermin can understand. All these creatures follow the Prince of Swarms’s orders and will never harm the devil.


  • Multiattack. The Prince of Swarms makes one bite attack and two claw attacks.
  • Bite. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 6) piercing damage plus 9 (2d8) poison damage. If the target is a creature, it must succeed on a DC 22 Constitution saving throw or be cursed with the Prince of Swarms rot. The cursed target is poisoned, can’t regain hit points, its hit point maximum decreases by 13 (3d8) for every 24 hours that elapse, and vermin attack the creature on sight. If the curse reduces the target’s hit point maximum to 0, the target dies and immediately transforms into a randomly chosen swarm of insects. The curse lasts until removed by the remove curse spell or comparable magic.
  • Claw. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 10 (1d8 + 6) slashing damage plus 9 (2d8) poison damage.
  • Vermin Breath (Recharge 5-6). The Prince of Swarms exhales vermin in a 120-foot line that’s 10 feet wide. Each creature in the line takes 54 (12d8) poison damage, or half damage with a successful DC 22 Dexterity saving throw. Each creature that fails this saving throw must succeed on a DC 22 Constitution saving throw or be cursed with the Prince of Swarms rot (see the Bite attack). In addition, the Prince of Swarms summons a swarm of insects (of any type) at any point of the line. The swarm remains until destroyed, until the Prince of Swarms dismisses it as a bonus action, or for 2 minutes. No more than five swarms of insects can be summoned at the same time.

Legendary Actions

The Prince of Swarms can take 3 legendary actions, 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. The Prince of Swarms regains spent legendary actions at the start of its turn.

  • Move. The Prince of Swarms moves up to half its speed, using any movement mode it wishes.
  • Poison. The Prince of Swarms targets a creature within 120 feet. If the target isn’t poisoned, it must make a DC 22 Constitution saving throw or become poisoned. The poisoned target repeats the saving throw at the end of each of its turns, ending the effect on itself on a success.
  • Spell (Costs 2 Actions). The Prince of Swarms casts a spell.


This insectile humanoid‘s mouth stretches over dripping mandibles that are poorly concealed behind an ill-fitting mask of flesh. Its eyes have compound irises, and barbed stingers sprout between the fingers at the ends of its long, segmented limbs.

Section 15: Copyright Notice

Tome of Beasts. Copyright 2016, Open Design; Authors Chris Harris, Dan Dillon, Rodrigo Garcia Carmona, and Wolfgang Baur.

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