"You cannot hide from what you once were, Revan! Recognize that you were once the Dark Lord — and know that I have taken your place!"
Apprentice to Revan, Malak and his master were renowned heroes of the Republic during the Mandalorian War. During the war, the two uncovered a Star Map on Dantooine, which led to their seeking out all the other Star Maps. Each of which would help them to locate the Star Forge, an ancient relic that served as a factory, self-perpetuating as it drew power from stars and the force to produce droids, ships, and other instruments of conquest. As their search spanned across the galaxy, Malak and Revan were influenced by the dark side of the force, leading them to seek out Sith teachings.
After their victory over the Mandalorians, Revan and Malak left for unknown regions of the galaxy, leading their Republic supporters to believe them dead. A year later, Malak and Revan returned, and finally found the Star Forge. The two then founded a Sith Academy on Korriban, which led to the duo openly revealing themselves as Sith Lords. The two then declared war upon the Republic, initiating the Jedi Civil War.
An initial disagreement between master and apprentice over how policies were being carried out led to a duel. Revan did not kill Malak, though he did cut off his lower jaw with his lightsaber, leading Malak to adopt the metallic face piece and the electronic tone that came along with it. As the years drew on in the conflict, Malak gained ownership of the flagship Leviathan, and promoted former Republic Admiral Saul Karath to be Commander of the entire Sith fleet. After testing Karath's loyalty to him, Malak began devising a way to surpass his master.
His chance came when the Republic sent a specialized team in to capture Revan and Malak. Wishing to destroy both his master and his Jedi foes in one fell swoop, Malak ordered his ship to fire upon Revan's. Believing his master dead, Malak still had one foe that he feared - Bastilla Shan. As Bastilla and a very-much-alive (though missing his memories) Revan set out for their own search for the Star Maps, Malak sent his apprentice Darth Bandon and mercenary Calo Nord to stop her, though both ultimately failed. Eventually, Malak and Karath encountered the Ebon Hawk, bringing Bastilla, Revan, and co. aboard to torture and question. The team quickly escaped, but not before an encounter with Malak made Revan's true identity as a former Sith Lord clear to him. Revan and the others escaped, intent on uncovering the final piece of the puzzle. But Bastilla was now Malak's captive and, after much torture, he managed to sway her to the dark side.
With the Star Forge operating beyond expectations, Malak built his army until Revan arrived to face him. Revan convinced Bastilla to return to the light side, then eventually defeated Malak. In his final moments, Malak reflected upon all of his actions as a Sith Lord, most notably his jealousy of Revan's grand role in the war and his cowardice at not having faced him in duel the first time Malak tried to kill Revan. Malak died not feeling hatred toward Revan, but still accepting the actions that had led him to the dark side as being his own.
Some of the tracks in Knights of the Old Republic break the traditional Star Wars formula to a significant degree. This track certainly feels like it is in keeping with the atmosphere of the game, but also has a classic Star Wars feel to it, along the lines of "Battle of the Heroes" or "Duel of the Fates".