pf2e.fyi
From Pathfinder #213: Thirst for Blood, which isn't enabled.

Camazotz's Swarm

COMPLEX HAZARD 1
Stealth +7 (trained)
Description A massive swarm of bats flies throughout the room, hampering vision, attacking foes, and magically restoring Camazotz's followers.

Disable DC 17 Nature (trained) to disperse the swarm or DC 15 Religion (trained) to disrupt Camazotz's connection, which disperses the swarm

AC 19; Fort +10, Ref +11
HP 26 (BT 13); Immunities critical hits, precision

Swarming Descent (divine, emotion, fear, mental)
Trigger A creature that's not a worshipper of Camazotz enters the room

Effect The hundreds of bats descend down into the room in a terrifying, shrieking mass. The swarm occupies a 30-foot burst on the floor of the room. All enemies within this area must attempt a DC 17 Will save. On a failure, a creature becomes Frightened 1 (Frightened 2 on a critical failure). The swarm then rolls initiative.
Restore Follower (divine)
Requirements An ally is in the swarm's space
Trigger The swarm dealt damage to an enemy

Effect The swarm takes some of the blood it drank from an enemy and feeds it to an ally in its space. The ally restores Hit Points equal to the highest damage the swarm dealt to an enemy this turn.
Routine (2 actions) The swarm uses its first action to move up to 30 feet to envelop as many enemies as possible within its 30-foot burst space. All enemies in the swarm's space become Dazzled while within the swarm. It then uses its second action to bite all enemies, dealing 1d6+3 piercing damage (DC 17 basic Reflex save) to all enemies in the space.
Reset The swarm disperses and returns to roost throughout the room 1 minute after all enemies leave the room. The swarm recovers 5 Hit Points per day thanks the power of Camazotz.
Pathfinder #213: Thirst for BloodORC