The story continues where Diablo II ended. Two of the Three Prime Evils, Mephisto and Diablo, have been defeated and their Soulstones have been destroyed, preventing their return. However, the narrator Marius was tricked into surrendering the last Soulstone to a false Archangel Tyrael which was revealed to be Baal, the third brother and the very last remaining Prime Evil. Marius was subsequently murdered.