THE NATURE OF SWARMS

The swarms presented here aren't ordinary or benign assemblies of little creatures. They form as a result of some sinister or unwholesome influence. A vampire can summon swarms of bats and rats from the darkest corners of the night, while the very presence of a mummy lord can cause scarab beetles to boil up from the sand-filled depths of its tomb. A hag might have the power to turn swarms of ravens against her enemies, while a yuan-ti abomination might have swarms of poisonous snakes slithering in its wake. Even druids can't charm these swarms, and their aggressiveness is borderline unnatural.

🦇 Bats

🦇 SWARM OF BATS	Medium swarm of Tiny beasts, unaligned
Armor Class	12
Hit Points	22 (5d8)
Speed	O ft., fly 30 ft.
STR	5 (-3)
DEX	15 (+2)
CON	10 (+0)
INT	2 (-4)
WIS	12 (+1)
CHA	4(-3)
Damage Resistances	bludgeoning, piercing, slashing Condition Immunities
Senses	blindsight 60 ft., passive Perception 11
Languages	-
Challenge	1/4 (50 XP)
Echolocation	The swarm can't use its blindsight while deafened.
Keen Hearing	The swarm has advantage on Wisdom (Perception) checks that rely on hearing.
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 bat. The swarm can't regain hit points or gain temporary hit points.
Actions
Bites	Melee Weapon Attack: +4 to hit, reach O ft., one creature in the swarm's space. Hit: 5 (2d4) piercing damage, or 2 (1d4) piercing damage if the swarm has half of its hit points or fewer.