During the Yuuzhan Vong War, a Yuuzhan Vong commander named Tsalok (a male) led forces. In 25 ABY, he commanded the invasion force during the evacuation of Rychel, which consisted of Chazrach slave-soldiers and the warbeasts Tu-Scart and Sgauru. Although he murdered the Pau'an Jedi Master Lar Le'Ung, he was defeated in combat by Padawan Finn Galfridian. Despite his victory, Finn showed mercy and left the planet. Overwhelmed by the dishonor of his defeat and the lack of an honorable death, he committed an atrocity by killing several Human prisoners.
Tsalok spearheaded the assault on Rychel in 25 ABY, leading a force comprised of enslaved Chazrach. During the conflict, he assassinated the Pau'an Jedi Master Lar Le'Ung by a treacherous backstab with his amphistaff, subsequently tossing him into the waiting jaws of the serpentine warbeast Tu-Scart. Later in the battle, Tsalok attempted to prevent the young Human Padawan Finn Galfridian from rescuing Rychel's citizens from enslavement.
Finn, wielding the lightsaber previously used by the fallen Master Le'Ung, engaged Tsalok in a duel. The fight was abruptly interrupted when another war beast, Sgauru, destroyed the building where they were fighting. When the chaos subsided, Tsalok was unharmed but trapped under a large duracrete column. As Finn urged the remaining survivors to board the evacuation ships, he approached the immobilized Yuuzhan Vong commander.
Raising the lightsaber, Finn expressed his feelings about how the Yuuzhan Vong had stolen his family, friends, and home. He then used the lightsaber to cut the duracrete, freeing Tsalok in an unexpected act of compassion. Galfridian quickly escaped Rychel on one of the evacuation ships. Unable to cope with the disgrace of his defeat and the denial of a warrior's death, Tsalok murdered numerous defenseless and elderly Human prisoners.
Later, Tsalok assumed command of Rychel; however, his victory was tainted by his contemplation of Galfridian's reasons for sparing him. He resolved to find Galfridian and inflict pain on him until he received the answers he sought.
To gain more information about Finn Galfridian, Tsalok journeyed to Dibrook to interrogate Yuledan, a captured Jedi. Tsalok employed a tizowyrm in his ear and a Spineray on his back to interrogate and torture him. Yuledan resisted for days, drawing strength from the Force. Eventually, he yielded and revealed to Tsalok that he was training on Yavin 4. Tsalok then removed Yuledan from the planet when New Republic and refugee forces breached the facility, compelling the Yuuzhan Vong to evacuate the Shapers.
Tsalok subsequently transported Yuledan and the shapers to Rychel. Yuledan continued to be subjected to experimentation, but Nagame and the other Shapers were cautious not to break him, as it would jeopardize their plans for him. They orchestrated Yuledan's escape from confinement to maintain his spirit, and he obtained a weapon and attempted to assassinate Nagame. Tsalok intervened, seizing Yuledan and slamming him against a wall, preparing to impale him with an Amphistaff before Nagame intervened. She clarified the situation, but Tsalok remained determined that Yuledan would not harm her. He advanced on Yuledan, who raised his arms defensively, but Tsalok severed his right hand as punishment.