The clash between the Dark Lord of the Sith Revan and his Sith apprentice, Darth Malak, known as the Duel on Darth Revan's Flagship, transpired amidst the Jedi Civil War. This lightsaber duel occurred on Revan's flagship, ultimately leading to Malak's failure and the disfigurement of his jaw.
During the conflict, Malak began to perceive his Master as weak, leading to friction between them. This discord eventually escalated into a lightsaber battle.
Revan's lightsaber strike severed Malak's jaw, necessitating the use of a large metal prosthesis cover to replace the missing bone. A vocabulator was implemented to enable Malak to speak, but his voice gained a harsh, mechanical quality.