Fire-Breathing Statue

From Dungeon Master's Guide, page 122.

Magical trap

This trap is activated when an intruder steps on a hidden pressure plate, releasing a magical gout of flame from a nearby statue. The statue can be of anything, including a dragon or a wizard casting a spell.

The DC is 15 to spot the pressure plate, as well as faint scorch marks on the floor and walls. A spell or other effect that can sense the presence of magic, such as Detect Magic, reveals an aura of evocation magic around the statue.

The trap activates when more than 20 pounds of weight is placed on the pressure plate, causing the statue to release a 30-foot cone of fire. Each creature in the fire must make a DC 13 Dexterity saving throw, taking 22 (4d10) fire damage on a failed save, or half as much damage on a successful one.

Wedging an iron spike or other object under the pressure plate prevents the trap from activating. A successful Dispel Magic (DC 13) cast on the statue destroys the trap.