Apollyon (5e Creature)
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Medium fiend, any evil alignment
Skills Arcana +3, Perception +5
Swarm Host. Upon falling to 0 HP, the Apollyon Swarm abandons this shell. Make sure to count the CR of the Swarm separately when calculating the challenge of encounters.
Innate Spellcasting The Apollyon's innate spellcasting ability is Wisdom (spell save DC 13). The Apollyon can cast the following spells without any material components:
Swarm Mind The Apollyon rolls at advantage to resist spell effects that effect the minds of a single target (i.e suggestion, or feeblemind, but not confusion), unless the caster is aware that the Apollyon is a mindless creature piloted by a swarm.
Multiattack The Apollyon can make two claw attacks.
Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 4) slashing damage.
The Apollyon is, in a sense, a mindless shell piloted by an Apollyon Swarm. The swarm, a single hivemind occupying a swarm of tiny fiendish bodies, is capable of consuming a humanoid's corpse, using it as scaffolding and materials to build a living, animated shell around it. The Apollyon Swarm does not care too much when its shell is destroyed, it can always make another.