From Pathfinder Society Scenario #1-08: Revolution on the Riverside, which isn't enabled.

Weak Spider Swarm

CREATURE -1

An abundance of food, the sudden hatching of a clutch of eggs, or magical influence can cause smaller spiders to gather in terrifying, deadly masses.

Few everyday vermin inspire as much dread as the infamous spider.

Perception +4; darkvision, tremorsense (imprecise) 30 feet

Skills Acrobatics +4, Athletics +1, Stealth +4

Str -2, Dex +3, Con +0, Int -5, Wis +0, Cha -4

Tremorsense (Imprecise) 30 feet (Creatures Touching its Web)

Tremorsense allows a monster to feel the vibrations through a solid surface caused by movement. It is an imprecise sense with a limited range (listed in the ability). Tremorsense functions only if the monster is on the same surface as the subject, and only if the subject is moving along (or burrowing through) the surface.

AC 14; Fort +3, Ref +6, Will +1

HP 8; Immunities precision, swarm mind; Weaknesses area damage 5, splash damage 5; Resistances bludgeoning 2, piercing 5, slashing 5

Swarm Mind

This monster doesn't have a single mind (typically because it's a swarm of smaller creatures), and is immune to mental effects that target only a specific number of creatures. It is still subject to mental effects that affect all creatures in an area.

Speed 20 feet, climb 20 feet

Spider Swarm Venom (poison)

Saving Throw DC 13 Fortitude

Maximum Duration 4 rounds

Stage 1 1 poison and Enfeebled 1 (1 round)

Stage 2 1d4 poison and Enfeebled 1 (1 round).

Swarming Bites

Each enemy in the spider swarm's space takes 1d4-1 piercing damage with a DC 13 basic Reflex save. A creature that fails its save is exposed to spider swarm venom.

Pathfinder Society Scenario #1-08: Revolution on the RiversideOGL