Lesser Cranium Rat Swarm (5e Creature)
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tiny swarm of medium monstrosities, neutral evil
Condition Immunities charmed, frightened, paralyzed, petrified, prone, restrained, prone, restrained, stunned.
Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move thru any opening large enough for a Tiny rat. The swarm cannot regain hit points or gain temporary hit points.
Bite. Melee Attack:+2 to hit, reach 0 ft., one creature in the swarm's space. Hit: 7 (2d6) piercing damage, or 3 (1d6) piercing damage if the swarm is at half points or fewer.
Mind Blast(recharge 5-6). The swarm emits a barrage of harmful psychic energy within a 60 ft cone. All non-cranium rats in the area must make a DC 10 Wisdom saving throw, or take 10 (3d6) psychic damage and be stunned until the end of their their next turn.
Merge. The swarm merges with another adjacent lesser cranium rat swarm, the two forming an average cranium rat swarm together.
Cranium rats appear as normal rats with exposed brains and a malicious gleam in the eye. Individually they pose no more of a threat than a common rat, but in large numbers they develop a hive-like awareness of pure malice and gain the ability to use limited magic. They are commonly found in settlements on the Lower Planes and their gate-towns, as well as the sewers of Sigil where it is rumored a powerful cranium rat hive mind comprised of hundreds lurks. Sages conjecture the cranium rats may be servants of Ilsensine or some other unfathomable power using them as spies.
A lesser cranium rat swarm has about 75 to 100 rats. An average cranium rat swarm has about 150 rats. A greater cranium rat swarm has 200 or more rats.