Fireball Rune Hazard 5

Pathfinder Core Rulebook (Second Edition), page 524

Stealth DC 24 (expert)

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

Disable Thievery DC 22 (expert) to erase the rune without triggering the sensor, or dispel magic (3rd level; counteract DC 20) to counteract the rune

Fireball ↩ (arcane, evocation, 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-level fireball spell that deals 6d6 fire damage (DC 22 basic Reflex save).