uncommon n large animal swarm 

Perception +5; darkvision

Skills Acrobatics +6, Stealth +4

Str -2 Dex +3 Con +0 Int -5 Wis +1 Cha -2

AC  13; Fort +5, Ref +8, Will +4

HP 9; Immunities precision, swarm mind; Weaknesses area damage 2, splash

Speed 40 feet, climb 20 feet

Swarming Bites [>] Each enemy in the silverfish swarm's space takes 1d4 piercing damage (DC 14 basic Fortitude save). A creature that fails its save is sickened 1.

Voracious Consumption (1 minute) A silverfish swarm consumes up to 1 Bulk of paper, cloth, or similar material. It can consume up to 4 Bulk each day.

Strength of Thousands #1: Kindled Magic, page 84.