Innate Spellcasting (1/Day). The mephit can innately cast heat metal (spell save DC 10), requiring no material components. Its innate spellcasting ability is Charisma

Death Burst. 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) 2d6 fire damage on a failed save, or half as much damage on a successful one.   False Appearance. While the mephit remains motionless, it is indistinguishable from an ordinary mound of magma.