The Kaggath represented an age-old, though infrequently practiced, custom amongst the Sith. Functioning as a combination of single combat and a grand dejarik game, the Kaggath pitted Sith against each other, with the stakes being utter humiliation or death.
During the era of the re-established Sith Empire, only a Sith recognized by the Dark Council as possessing adequate strength and influence held the authority to initiate a Kaggath. A Sith could issue a challenge to another for any reason, encompassing conflict, rage, retribution, avarice, or simple animosity. The challenger designated the battleground, potentially a planet, a star system, or even the entire galaxy, and upon acceptance by the challenged, the ritual commenced.
The two adversaries marshaled their complete military resources, including armies, bases, and starships, aiming to outsmart and outmaneuver their rival in order to achieve total victory.
These conflicts were to be waged without external assistance, as a direct test of one Sith's prowess and resources against another's. Violating any tenet of the rite typically resulted in the offender's execution by other Sith not involved in the particular Kaggath. Refusal to accept a Kaggath resulted in the challenging Sith acquiring the rank of the one who declined.
The Kaggath concluded upon the defeat or surrender of one side, granting the victorious Sith the choice of either killing their opponent or allowing them to live with the burden of shame. Furthermore, the victor could seize all assets, including military forces, from the defeated combatant or opt to destroy them. The triumphant Sith also gained the power to obliterate their opponent's name and erase their records from history, effectively eliminating any chance for the loser to leave a legacy, leading to a complete erasure of the defeated from memory.
According to Darth Thanaton, historical Sith Lords such as Tulak Hord, Marka Ragnos, and Ludo Kressh engaged in Kaggaths at different times. Upon his victory in his Kaggath, the Dark Lord of the Sith Tulak Hord commanded that his opponent's name be stricken from all records.
Darth Qalar and Darth Victun, both members of the Dark Council, once participated in a Kaggath that resulted in the destruction of the Imperial Citadel, leading to their execution by the remaining members of the Dark Council as punishment.
At some point, Darth Tormen triumphed over Lord Fatalissar in a Kaggath held on the world of Ziost, after his opponent named the arena in which it would take place, before the event began.
During the Cold War, Thanaton challenged the allegedly corrupt Sith Lord Kallig to a Kaggath. During a duel on Corellia, Kallig gained the advantage, forcing Thanaton to retreat to Korriban in pursuit of assistance from the Dark Council. Kallig pursued Thanaton and concluded their duel within the Dark Council chamber, leaving Thanaton near death to be executed by Darth Mortis for violating the rules of the ritual by seeking outside help.