Lucion

From Diablo Wiki

Lucion is the son of Mephisto, the Prime Evil from Act III of Diablo II, and the brother of Lilith, the uber-demon from the special Battle.net version of Diablo II's Tristram. His role in the Diablo universe predated the game series, but he was the main antagonist in the first novel of The Sin War trilogy, Birthright.

The Sin War: Birthright

Great Evils
Prime Evils	Baal • Diablo • Mephisto
Lesser Evils	Andariel • Azmodan • Belial • Duriel
Other Evils	Lilith • Lucion • Kabraxis • Xazax • Astrogha • Assur • Gulag