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From Pathfinder Adventure: The Slithering, which isn't enabled.

Stalker Summoning Rune

COMPLEX HAZARD 7
Stealth +15 (expert)
Description The sand conceals a rune that summons an invisible stalker into this yard.

Disable DC 25 Acrobatics to approach without triggering the trap followed by DC 25 Arcana (expert) or DC 27 Thievery (expert) to erase the rune, or Dispel Magic (4th rank; counteract DC 25) to counteract the rune


Summon Monster (arcane, summon)
Trigger A creature that isn't openly bearing an Aspis Consortium badge crosses the center of the yard

Effect The trap summons an Invisible Stalker. The invisible stalker rolls initiative and remains for 2d6 rounds, after which the spell ends and the invisible stalker disappears. The invisible stalker also disappears if someone disables the trap before the duration expires.

The invisible stalker can use 3 actions each round and can use reactions, unlike most summoned creatures.

Reset The trap resets after 24 hours.
Pathfinder Adventure: The SlitheringOGL