In Diablo III: Reaper of Souls, Malthael becomes the main antagonist.
Malthael was formerly the Archangel of Wisdom and a member of the Angiris Council. After the destruction of the Worldstone and the escalating conflict between Heaven and Hell, he abandoned his former role and became the Angel of Death. He leads the Reapers, forces that harvest human souls.
The expansion’s campaign follows the aftermath of Diablo III’s original story. Malthael seeks to eliminate humanity because humans carry both angelic and demonic ancestry. This goal makes the Nephalem, the player character, central to the conflict. The campaign culminates in the battle against Malthael in the Pandemonium Fortress.
Malthael is sometimes confused with Tyrael, another important angel in the series. Tyrael remains an ally and former Archangel of Justice, while Malthael is the expansion’s principal enemy. Reaper of Souls also introduced Act V and the Crusader class.