Fireball Rune
HAZARD 5 +14 (expert)
An invisible rune creates an invisible, spherical magical sensor with a 20-foot radius.
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)
A living creature enters the sensor area
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 save).
Pathfinder GM CoreORC