Duel between Kas'im and Na'daz

In the years leading up to Lord Kaan's ascension, the Sith Empire was plagued by internal conflicts, with Sith Lords constantly seeking to prove their superiority against worthy opponents; often each other. Amidst this chaotic environment, Kas'im entered the scene, taken from his enslaved parents as an infant and placed under the tutelage of the Sith Lord Na'daz. Na'daz, a master of lightsaber combat, trained his apprentice to become equally proficient. As time progressed, Kas'im grew restless under Na'daz's guidance, believing he had absorbed all he could from his master, and subsequently challenged him to a duel.

The specific location and duration of the duel remain unknown, but Kas'im emerged as the ultimate victor. In his own words, Although my master was strong in the Dark side, I was stronger. Although he was skilled with the lightsaber, I became better. Kas'im considered the battle a personal trial of strength. He claimed Na'daz's lightsaber as a symbol of his victory.

Kas'im later aligned himself with the Brotherhood of Darkness founded by Lord Kaan, assuming the role of lightsaber instructor at the Sith academy on Korriban. A decade after the duel, he recounted the story to his star pupil, Bane, and gifted him Na'daz's lightsaber. By this point, while Kas'im felt no remorse for killing his master, he recognized the act as imprudent, having embraced the Brotherhood's doctrines; while he demonstrated his personal power, he ultimately weakened the Sith Order by eliminating one of their most formidable duelists.

Bane would later draw inspiration from this duel for his Rule of Two, a new Sith structure limiting the Sith Lords to only two at any given time; a master and an apprentice. To implement this new order, Bane orchestrated the downfall of the Brotherhood of Darkness during the Seventh Battle of Ruusan. He personally ended Kas'im's life during their Duel on Lehon, viewing it as a personal test of his own abilities.