The Krath Holy Crusade (3997 BBY-3996 BBY) represented a sequence of conflicts occurring both before and during the Great Sith War, essentially forming the core of that larger war. This crusade marked the culmination of a series of events that originated with a forceful political_uprising_of_the_empress_teta_system within the Empress Teta system. This uprising was orchestrated by Aleema and Satal Keto, who were not only heirs to the Tetan monarchy but also leaders of the Sith-influenced Krath cult. Following the conclusion of the war, the Krath order proceeded to construct a number of temples across several of the worlds they had conquered during the Crusade. This Crusade's beginning coincided with the Mandalorians launching their own holy crusade against the Basiliskans on Basilisk, and its end came after the defeat of Dark Lord of the Sith Exar Kun on Yavin 4.
In 3998 BBY, two young aristocrats from the Empress Teta system journeyed to Coruscant. These were Satal Keto and his relative Aleema, the designated successors to the Tetan throne, undertaking what could be described as a vacation to the galactic capital. Upon their arrival on the capital planet aboard their royal vessel, aptly named the Krath Enchanter, the Ketos initiated their visit with a tour of Coruscant's Galactic Museum.
However, their real purpose for visiting Coruscant was to seek out knowledge regarding the ancient Sith, particularly anything pertaining to the dark side. Coincidentally, at the time of the Ketos' arrival, the museum was nearing completion of a new exhibit centered on the dark side, appropriately titled "Dark Lords of the Sith". The Ketos eagerly requested permission to explore the unfinished exhibit, but the curator hesitated due to explicit instructions from the Jedi Order that the hall remain off-limits until adequate security measures were in place.
Despite the curator's initial reluctance, the Ketos persisted in their request, eventually persuading the curator to grant them access. They were then permitted to enter a hall dedicated to the Sith, filled with ancient and invaluable artifacts, texts, tomes, and amulets, all emanating with dark side energy. This energy was palpable to Satal and Aleema through the Force. They swiftly pilfered one of the books and retreated to their lodging. Frustrated by their inability to decipher the book's contents, the Ketos' spirits were lifted upon hearing a news report about dark side adepts on Onderon who practiced ancient Sith magic. Recognizing that Onderon held the key to unlocking the secrets of the book, they immediately departed Coruscant, setting course for the dark side world.
The Krath's military forces initiated an assault on Koros Major, the last remaining free planet. Aleema aided her forces by employing her Sith powers. Fortunately, a Republic detachment entered Koros Major's space to reinforce the struggling planet. However, space grazers, previously thought to be extinct myths, suddenly appeared. Jedi Knight Nomi Sunrider discerned the illusions and instructed the Republic forces to disregard them and focus on the stations.
Satal played his trump card against the Republic by deploying the chaos fighters. Nomi, assuming they were all illusions, telepathically attacked Aleema, who was generating some of the illusions, thus distracting her. However, Nomi failed to realize that most of the fighters were real. These fighters then executed kamikaze attacks on the Republic forces, compelling them to retreat.
In the meantime, the Krath were reveling in their recent triumph over the Republic. Back at their Iron Citadel stronghold, Satal Keto cared for his cousin Aleema, who had been rendered comatose by Nomi Sunrider's psychic assault. Upon regaining consciousness, Satal quickly updated Aleema on the current state of affairs. He informed her that the Jedi and Republic fleet had been repelled, thanks to the power of Sith magic. He also informed Aleema about the Jedi convocation scheduled to take place on Deneba. Satal had managed to position one of his Tetan Corsairs in orbit around Deneba in preparation for the next phase of his plan. At a time of Lord Keto's choosing, the Corsair would unleash its full complement of life-pods, each carrying an assortment of Krath war droids. The second part of the attack would target the planet's surface; Satal intended to turn the Jedi's service droids against them, overwriting their original programming with that of his own Krath war droids. Once the life-pods were deployed, a signal would be transmitted from the Corsair, activating the service droid's programming trap. Communicating with the Corsair captain via comlink, Lord Keto instructed him to commence the assault.
The Jedi barely managed to evade the ambush, even as Cay's servant droid met a swift end at the blade of Nomi Sunrider's lightsaber. However, Cay's was not the only droid affected by the programming trap. All of the Conclave server droids received the Krath transmission and immediately began attacking their Jedi masters. Cay thanked Nomi while reminding everyone that he warned them of the droids' suspicious behavior. Much to his horror, his suspicions were confirmed as he and the other Jedi were forced to evade heavy blaster fire. Furthermore, Krath war droids were emerging from the wreckage of the life-pods.
The Jedi directly engaged the droids, leaving hundreds of lightsaber-cleaved droids scattered across the battlefield. Master Jeth demonstrated a subtle application of the Force to reach inside the droids and disable their internal mechanisms. Many more droids were disabled by Master Arca's droid disabling technique, which Ulic praised. However, as he spoke, a war droid blindsided him, preparing to deliver the final blow. But Arca, aware of Ulic's danger, once again used the Force to destroy the droid. As he turned his attention to speak to Qel-Droma, one of the downed droids activated its secondary systems and fired a blaster shot into Jeth's back, felling the Jedi Master. Standing behind him was the war droid he had just saved Ulic from, blaster still raised and smoking. As the droid mocked them, Qel-Droma succumbed to his rage and destroyed the droid. He then rushed to his Master's side, to hear Arca's final words of wisdom and encouragement: to fight the dark side, not embrace it. Arca told his former apprentice that he possessed a weapon that the darkness could not withstand: the power of the Light. He then became one with the Force, leaving only his Jedi robes behind.
Believing that the only way to defeat the Krath was to infiltrate their ranks, Ulic proposed that he personally infiltrate them. Although the Jedi Masters were horrified by the idea, they reluctantly agreed to allow him to try. However, before he departed, Master Odan-Urr showed him, through a Sith holocron, how the Sith spend their lives—literally.
Qel-Droma's arrival in Cinnagar did not go unnoticed; the Krath were well aware of his presence. He was prepared to kill the young Jedi but Aleema just told him to wait. The next day, she was ready to execute a prisoner when the crowd began rioting.
Concerned about Ulic, Nomi spearheaded a mission to Cinnagar to rescue him. She allowed herself to be captured, just as Ulic was helping the Tetans advance their technologies. Suspicious, Satal had Nomi brought before Ulic and was going to execute her, but Qel-Droma said that he would do it himself the next morning to maintain his cover. He sent a service droid with a message still detailing his mission to Nomi; however, it was intercepted by Satal. Furious at this betrayal, Satal ordered his servant Norgor to kill Ulic and have Nomi brought to him. Ulic was not caught off guard after sleeping with Aleema, though. He learned of Satal planned attack at Deneba. Enraged, he decided to search for Satal as Nomi escaped the dungeons.