Achernonian

A purple-grey-skinned humanmoid race native to the planet Achernon, fourth planet orbiting Alpha Unakalhai. Achernonians are a tall race, averaging 6'4" tall, and possess only a pre-Industrial level of technology. They are depicted as superstitious and hedonistic, with a dictatorial government. Some possess the ability to become immaterial at will, though it is unknown how common this ability is or what causes it. The planet Achernon is a rocky world, 60% covered in volcanic rock; the atmosphere possesses a high sulfur content.

Behind the scenes
They were first seen in Thor Annual #6 (1977). The name of the planet/race may have been derived from the Greek river Acheron.