Mephistians are a race of xenoforms bred by the Rebel Faction of angels for use as hosts. They are muscular, red-skinned humanoids with batlike wings and horns. Their eyes are luminous red with black reptilian pupils. Use of Mephistians is so common amoungst the Rebel Faction that they are the popular image of "devils" in the public consciousness. Unpossessed Mephistians are docile, slightly dim creatures, easily intimidated in spite of their great size and strength. Although their digestive system can handle meat, the unpossessed Mephistians subsist almost entirely on nuts, berries and leaves.

As Mephistians age they grow larger and stronger and their skin grows thicker and darker. Young adult Mephistians are typically 6 feet tall with bright red skin. By the time they are 200 years old their skin has darkened to a deep maroon and they stand about 7 feet tall. The oldest of the Mephistians, who are about 500 or 600 years old, have jet black skin and stand between 8 and 9 feet tall. Mephistians never die of old age, but due to the risky nature of their lives as hosts, it is uncommon that they live into their third century. There are less than 20 Black Mephistians and the use of such a host is a highly prized status symbol amoungst senior Rebels.

Mephistians are one of Belial's pet projects.