The Archbishop Lazarus was an ambassador from the Zakarum Church and an advisor to King Leoric. Lazarus was the Custodian of Mephisto's Soulstone in Kurast sometime prior to his arrival in Khanduras. When King Leoric set up court in the abandoned Monastery, Lazarus was lured into the monastery's depths by Diablo, where Lazarus proceeded to shatter the soulstone that imprisoned the Prime Evil. After Diablo failed to fully possess King Leoric himself, Lazarus brought the King's son, Albrecht, into the labyrinth to serve as the mortal host for the Lord of Terror. After King Leoric's death, Lazarus emerged from the Monastery and whipped the villagers into a frenzy to find Albrecht - but the treacherous Archbishop led them right into the lair of the Butcher.
After this disastrous incursion, Lazarus vanished deep into the Monastery, where he remained. He is later defeated by the hero in Diablo.
His staff, the Spire of Lazarus and the dagger Wizardspike (sometimes dropped upon his defeat), are both unique items in Diablo II, although Lazarus's staff was not able to be wielded in the first game, serving only as a key to the cathedral's tower where Lazarus resided.