Guuthal

 was an ancient black dragon and a dracolich during the Age of Arcanum.

Appearance
All that is known of Guuthal's appearance is that he was a particularly ancient and mighty black dragon as his life was unnaturally extended.

Vex'ahlia read about this ancient black dragon in Opash's journal. It was through a necromantic ritual that Guuthal became a dracolich, terrorizing the world in the Age of Arcanum. Through the means of ritualistic aid, forbidden rites, and sacrificing his own life force, he achieved his goal to be born again as a never-dying new form of unlife.