The Kaggath was an ancient, but rarely employed, rite of the Sith. One part duel, one part large-scale dejarik-match, the Kaggath pitted Sith against Sith unto humiliation and death.
During the rule of the reconstituted Sith Empire, only a Sith who was recognized by the Dark Council as having sufficient power and authority could declare a Kaggath. One Sith could challenge another Sith for any reason, be it strife, anger, vengeance, greed or pure dislike. The challenger set the arena, whether a planet, a star system or the entire galaxy, and if accepted by the challengee, the ritual began.
The two combatants employed the full force of their armies, bases and ships to outwit and outmaneuver their opponent in an attempt to defeat each other's forces.
The battles had to be fought without any kind of outside help, in a direct confrontation of one Sith's power and assets against another's. The breach of any rule of the rite usually resulted in the execution of the offender by other Sith not involved in that particular Kaggath, If one declined a Kaggath the Sith who challenged the other Sith would get his or her rank.
The Kaggath reached a conclusion when one side was defeated or had surrendered, with the triumphant Sith choosing whether to terminate his opponent or leave him alive with the weight of humiliation. The winner also had the option to absorb all the properties, along with the military assets, of the loser combatant or choose to destroy them. Furthermore, the Sith who prevailed in the Kaggath also had the right to destroy his opponent's name and wipe their records from recorded history, theoretically eliminating any chance for the loser to leave some form of legacy to the rest of the galaxy, resulting in a complete deaminated memory of the defeated.
According to Darth Thanaton, Sith Lords such as Tulak Hord, Marka Ragnos, and Ludo Kressh have competed Kaggaths at various points. Upon winning his Kaggath, the Dark Lord of the Sith Tulak Hord ordered for the name of his opponent to be erased from history.
Darth Qalar and Darth Victun, members of the Dark Council, once participated in a Kaggath that destroyed the Imperial Citadel, and they were executed by the rest of the Dark Council as punishment.
At some point in his life, Darth Tormen defeated Lord Fatalissar in a Kaggath on the planet Ziost, as his opponent was naming 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 won the upper hand, causing Thanaton to flee to Korriban to seek the aid of the Dark Council. Kallig followed Thanaton and finished the duel in the Dark Council chamber, leaving Thanaton near-death to be brutally executed by Darth Mortis. This was due to Thanaton breaking the rules of the ritual in an attempt to ask for help.
- Star Wars: The Old Republic Encyclopedia