Magma Mephit

When the mephit dies, it explodes in a burst of lava. Each creature within 5 feet of it must make a DC 11 Dexterity saving throw, taking 7 (2d6) fire damage on a failed save, or half as much damage on a successful one.

While the mephit remains motionless, it is indistinguishable from an ordinary mound of magma.

The mephit can innately cast heat metal (spell save DC 10), requiring no material components. Its innate spellcasting ability is Charisma.

At will: heat metal

Melee Weapon Attack: +3 to hit, reach 5 ft., one creature. Hit: 3 (1d4 + 1) slashing damage plus 2 (1d4) fire damage.

The mephit exhales a 15-foot cone of fire. Each creature in that area must make a DC 11 Dexterity saving throw, taking 7 (2d6) fire damage on a failed save, or half as much damage on a successful one.