Source Bestiary pg. 347
A swarm is a mass or cloud of creatures that functions as one monster. Its size entry gives the size of the entire mass, though for most swarms the individual creatures that make up that mass are Tiny. A swarm can occupy the same space as other creatures, and must do so in order to use its damaging action. A swarm typically has weakness to effects that deal damage over an area (like area spells and splash weapons). Swarms are immune to the grappled, prone, and restrained conditions.


Algea, Amoeba Swarm, Animated Silverware Swarm, Army Ant Swarm, Bhanyada Swarm, Bloodseeker Swarm, Bone Skipper Swarm, Bore Worm Swarm, Brood Leech Swarm, Centipede Swarm, Clacking Skull Swarm, Cobblebone Swarm, Cobbleswarm, Cockroach Swarm, Consonite Choir, Ether Sprite Swarm, Fen Mosquito Swarm, Feral Skull Swarm, Fire Jellyfish Swarm, Flea Swarm, Gibtas Spawn Swarm, Hellwasp Swarm, Hermit Crab Swarm, Karumzek Swarm, Larval Cave Worm Brood, Monkey Swarm, Penqual, Phalanx Of Phalanges, Piranha Swarm, Rat Snake Swarm, Rat Swarm, Raven Swarm, Scorpion Swarm, Seetangeist, Silverfish Swarm, Skin Beetle Swarm, Sorcerous Skull Swarm, Spider Swarm, Sportlebore Swarm, Squirrel Swarm, Sturzstromer, The Bloodstorm, Tick Swarm, Tooth Fairy Swarm, Trapjaw Tangle, Trilobite Swarm, Vampire Bat Swarm, Viper Swarm, Wasp Swarm, Wizard Sponge, Worm That Walks Cultist