Dangerous Simple Trap (Levels 5–10)

Anyone who steps on the mosaic causes fire to erupt from it. 

Trigger. A mosaic on the floor of the entryway to the inner sanctum delivers a fiery rebuke to intruders.

Effect. A 15-foot cube of fire erupts, covering the pressure plate and the area around it. Each creature in the area must make a DC 15 Dexterity saving throw, taking 24 (7d6) fire damage on a failed save, or half as much damage on a successful one.

Countermeasures. A successful DC 15 Wisdom (Perception) check reveals the presence of ash and faint burn marks in the area affected by this trap. A successful DC 15 Intelligence (Religion) check enables a creature to destroy the trap by defacing a key rune on the perimeter of the mosaic that is within reach; failing this check causes the trap to activate. A successful Dispel Magic (DC 15) cast on the runes destroys the trap.