Tal Rasha was a powerful Horadric mage who led the campaign for hunting down and capturing the Prime Evil Baal. The Horadrim caught up with Baal near the desert city, Lut Gholein, and although they where eventually able to subdue the demon, the Soulstone that was meant to imprison him shattered in the process. The remaining shards of the Soulstone still behaved as the original one, but were not big enough to contain the essence of Baal for very long. Realizing that, Tal Rasha theorized that a mortal of strong will should be able to contain Baal within his own soul, dooming that man to wrestle with the demon for all eternity. Tal Rasha volunteered himself for the process, guided by the Archangel Tyrael, his fellow Horadrim were led to a secret tomb, one of seven tombs located in the Canyon of the Magi, there they had built a great binding stone, and chained their leader to it. After being bound to the stone, the fragment of the Soulstone containing Baal was pierced through the chest of Tal Rasha by the Archangel Tyrael, thus completing the prison.
In Diablo II the Dark Wanderer and Marius find Tal Rasha's tomb. Tyrael stops the Wanderer from reaching Baal, however, Marius ends us removing the stone from Tal Rasha's chest and releases Baal. He is still in possession of Tal Rasha's body allowing him access to all of Tal Rasha's power and knowledge. At the End of Act V, Tal Rasha's body is destroyed.
A Diablo II item set is also named after him, Tal Rasha's Wrappings.