From Pathfinder #210: Whispers in the Dirt, which isn't enabled.

Enhanced Fireball Rune

HAZARD 10

Stealth +22 (expert)

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

Disable DC 32 Thievery (expert) to erase the rune without triggering the sensor, or Dispel Magic (6th rank; counteract DC 27) to counteract the rune

Fireball

Trigger A living creature enters the sensor area

Effect The rune detonates a fireball centered on the triggering creature's square. This is a 6th-rank Fireball spell that deals 12d6 fire damage (DC 29 basic Reflex save).

Pathfinder #210: Whispers in the DirtORC