From Pathfinder Society Scenario #4-09: Killer in the Golden Mask, which isn't enabled.

Fireball Rune

HAZARD 5

Stealth +14 (expert)

Description An invisible rune creates an invisible, spherical magical sensor with a 20-foot radius.

Disable DC 22 Thievery (expert) to erase the rune without triggering the sensor, or Dispel Magic (3rd rank; counteract DC 20) to counteract the rune

Fireball (arcane, fire)

Trigger A living creature enters the sensor area

Effect The rune detonates a fireball centered on the triggering creature's square. This is a 3rd-rank Fireball spell that deals 6d6 fire damage (DC 22 basic Reflex).

Pathfinder Society Scenario #4-09: Killer in the Golden MaskOGL