Mephits are the varlets, lackeys, messengers, errand runners, and fetchers of the Lower Planes. They can be found in any of the evilly-aligned lower planes and will be serving the various demons, devils, evil elemental gods, or any extra-planar creature of dark purpose and evil intent. Their exact origins and home plane are not known; even the mephits themselves do not know for certain.

Mephits share various common characteristics. They are all about 5-ft tall, bat-winged, with sharp fangs. Mephits speak their own language shared by all the different types of mephits, their alignment tongue, and usually speak the common tongue of whatever lower plane they happen to call home. Mephits are mischievous and have a malignant sense of humour, finding joy in the pain of others. Mephits love to dress in outlandish clothing, choosing colours and designs that clash and draw attention. They are often found smoking an infernal cigar that gives off an offensive odour. Mephits love to strut about as they smoke, shrieking in shrill voices in their harsh tongue.

Fire mephits are a dull red colour with spots of black on the dorsal surfaces and a slightly lighter red on the ventral surface. Fire mephits are wreathed with tiny wisps of flame and touching one bare-handed will cause 1 point of damage. In combat mephits attack with two claws and a breath weapon. Though damage for claw attacks is listed as 1d3 points apiece, an additional 1 point of heat damage is also inflicted upon non fire-resistant opponents for a total of 2-4 points of damage per claw.