Mortamor

Mortamor is the true antagonist of Dragon Quest VI. He is the master of the four dread fiends; Murdaw, Jamirus, Gracos and Dhuran. Each of them was sent to seal a strategic location in the Dream World that gave people hope and terrorize the Real World inhabitants at the same time, all of this in order to conquer both worlds.

While it has multiple forms, they often resemble a red demon. According to its DQIX description, nobody knows how he really looks like.