Diablo II: Lord of Destruction (commonly abbreviated LoD) is an expansion pack for the hack and slash action role-playing game Diablo II. Unlike the original Diablo's expansion pack, Diablo: Hellfire, it is a first-party expansion developed by Blizzard North.
More than a standard expansion, Lord of Destruction not only added content in the form of two new character classes, new weapons and an addition of a fifth act, but also dramatically revamped the gameplay of the existing Diablo II for solo and especially multiplayer.
With the destruction of two of the Prime Evils, the Archangel Tyrael opens a portal to Harrogath, a stronghold on Mount Arreat in the northern Barbarian Highlands, to assist the adventurers in defeating Baal (who is in possession of his own Soulstone). Baal has raised an army and attacked the Barbarian inhabitants of Mount Arreat tasked with defending the Worldstone.
The adventurers ascend Mount Arreat while assisting the people of Harrogath.
They kill Elder Nihlathak for granting Baal access to the Worldstone Keep. And the player, after passing the test of the ancients at Mount Arreat, gains access to the keep. After defeating Baal's pack of minions at the Throne of Destruction, they engage Baal in the Worldstone Chamber and defeat him. The Archangel Tyrael appears after Baal's defeat but with the Worldstone corrupted by Baal, Tyrael has no choice but to destroy it.