DIABLO, THE LORD OF TERROR, is the most powerful of the three Prime Evils, despite being the youngest of the brothers. The other two being Mephisto and Baal.
In his previous incarnations on Sanctuary, Diablo has possessed a human vessel and transformed the host body. These humanoid forms have a number of features in common: a pointed chin, sharp teeth that protrude from bony gums, and a pair of horns that curve upward.
His true form could be vastly different. In the lore of the ages, it is said that Diablo takes the form of his viewer’s greatest fear. According to one source, he once terrified himself with his own reflection.
Some sources make reference to an almost insectoid or reptilian true form for Diablo, with overlapping plates or scales of skin and a deadly tail or tentacle.
More contemporary reports theorize that the lord has been affected permanently by the time he has spent in Sanctuary, his forehead scarred by an enduring gash where the Soulstone was embedded.