Swarm Attack
The creature automatically deals the listed damage to each creature whose space it occupies at the end of its turn with no attack roll needed. Swarm attacks aren’t subject to a miss chance for concealment or cover.
Format: Melee swarm attack (1d6+2 P).
Guidelines: To determine the amount of damage a creature of CR 6 or lower deals with swarm attack, use the value listed in the CR 6 Three Attacks entry on its appropriate array table, lowering the additional damage from that CR to match its actual CR. For all other creatures, use the Four Attacks entry for its CR in the corresponding array table.
Source
Alien Archive pg. 136