In Diablo II, which demon lord is the boss of Act III?

In Diablo II, Mephisto is the demon lord who serves as Act III’s boss.

Mephisto is the Lord of Hatred and one of the three Prime Evils, alongside Diablo and Baal. Players confront him in the Durance of Hate beneath the city of Kurast, after progressing through the jungle region and defeating compelling enemies such as the Council.

Mephisto’s defeat is a major turning point in the game’s story. His Soulstone can be destroyed in the Hellforge, but Diablo II’s campaign continues because the remaining Prime Evils still threaten Sanctuary. A common mix-up is confusing Mephisto with Diablo, who is the Act IV boss, or Baal, who is the final boss of the original Diablo II campaign’s Act V expansion content.

Mephisto also appears in later Diablo games and is central to Diablo IV’s storyline, where his influence is connected to Lilith and the wider conflict between the High Heavens and Burning Hells.