Tal Rasha was a powerful Horadric mage and leader of the Horadrim who sacrificed himself to forever encapsulate Baal in the dunes of Aranoch.
Contents
Background
Tal Rasha led the campaign for hunting down and capturing the Prime Evils, including Baal during the last Sin War. When the Prime Evils were exiled from Hell into the Mortal Realm by the Lesser Evils a group of mages brought together by the Archangel Tyrael organised themselves as te Horadrim and in order to defeat them and bind them to Soulstones which were provided by Tyrael.
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 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, dooming Tal Rasha to struggle for eternity against Baal.
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.
Other NPC's opinions
The Summoner lauds Tal Rasha and calls him "the foremost" of all of the Horadrim. Similarly on the eve of the final battle with Baal-cum-Tal Rasha, Deckard Cain makes clear his respect for the sorcerer:
"Remember this: Baal once possessed Tal Rasha, one of the most powerful of the ancient Horadrim. Your battles with Diablo and Mephisto will pale in comparison to your battle with Baal. The Lord of Destruction, aided by Tal Rasha’s knowledge… Ungh, the mountain itself will tremble when you clash!"
Two other Act II NPC's are not quite so supportive of Tal Rasha's decision however. Fara tells us that "his was a selfless act, although perhaps foolhardy." and Lysander, seeing the evil which plagued Lut Gholein muses that Tal Rasha's battle against evil was lost.
Diablo II
By the time the Dark Wanderer had reached Baal's prison, the demon had long since taken full control of the ancient mage, absorbing all his skills.
In Diablo II Act III a cinematic titled Mephisto's Jungle plays the arrival of the Dark Wanderer and Marius to Tal Rasha's secret tomb within the Canyon of the Magi. Below is the transcript of what happens:
Marius: "My companion drew in the dank, cold air of the tomb. It seemed to...strengthen him. I stood in the doorway between light and dark, what was left of my sanity implored me not to enter. But that voice was just a whisper now. As we worked our way down deeper and deeper into the crypt, I began to see a change in my companion. He seemed to be gaining strength. I could hardly see in the gloom, but my companion seemed to know the way. We came at last to a great hall."
(The Dark Wanderer screamed like an unholy creature from beyond this world. His face skin shifted oddly, as if transforming.)
Marius: "It was then I realized my companion hadn't been gaining strength. He had been losing what was left of his humanity. He moved at demonic speed, and then ... and then you appeared."
Before the Dark Wanderer could reach the soulstone on Tal Rasha's chest, Tyrael held his hand with his long wings and engaged in combat, plunging into the abyss below.
Tyrael: "Stop! The beast contained herein shall not be set free. Not even by you."
Baal: "Look, what have been done to me! Release me! Help me! Hurry, please, hurry!"
Baal lured Marius with a facade image, asking for help. Marius could only see a poor man bounded by chains, impaled by an object on the chest. Tyrael's gaze turned around toward Marius.
Tyrael: "NO !!! Don't do it!"
Marius grabbed the shattered soulstone shard and pulled it free from Tal Rasha's body.
In the blink of an eye, Tyrael released the Dark Wanderer and held Marius high above the ground.
Tyrael: "Fool, you have just insured the doom of this world. You cannot even begin to imagine what you set in motion this day. Go to the Temple of Light, in the eastern city of Kurast. There you will find the gate to Hell open before you. You must find the courage to step through that gate, Marius. Take the stone you hold to the Hellforge where it will be destroyed. Now run !!! Take the stone and run!"
From behind, Baal wrapped his tentacles around Tyrael's arm, letting his grasp on the Azureblade set loose.
Marius: "What choice did I have? I ran."
Items
Tal Rasha inspired one of the few most powerful sets of Diablo II items which have Display Auras: Tal Rasha's Wrappings.