is the main antagonist of Diablo: Hellfire, the first expansion of the original Diablo game - he was once an agent of Diablo but was cast into the abyss by his former master under unknown circumstances and later summoned to Earth by a foolish sorcerer whom he ultimately killed.

Na-Krul began unleashing hordes of new and powerful demons into the world while making a crypt his stronghold. Eventually he is fought as the final boss - with Na-Krul's defeat, his hordes presumably perish and the world is given some relief from demonic invasion (at least until Diablo II, that is).

Diablo Villains

The 7 Great Evils
Andariel | Azmodan | Baal | Belial | Diablo | Duriel | Mephisto

Other villains
Adria | Archbishop Lazarus | Blood Raven | Cydaea | Ghom | Izual | Maghda | Malthael | Na-Krul | Nihlathak | Skeleton King | Tathamet | The Butcher | The Dark Wanderer | The Summoner | Warlord of Blood | Zoltun Kulle