Tristan is a knight originally serving King Arthur as a member of the Knights of the Round Table. Renowned for exceptional archery skills and a melancholic nature, he bears the epithet "Tristan the Lamenting." After Camelot's fall and the perceived failure of its ideals, profound grief and disillusionment led him to embrace the philosophy that "there is no evil in the world," justifying inaction and moral detachment.

Within the Lion King's singularity, Tristan serves loyally among surviving Round Table knights, enforcing the decree to select only "pure" humans for the holy city while expelling or eliminating the unworthy. He accepts this path under his belief that no choice is inherently evil. A pivotal confrontation occurs with Bedivere, another knight upholding Arthur's original ideals. Witnessing Bedivere’s unwavering conviction and defense of the innocent forces Tristan to confront the suffering caused by the Lion King’s rule.

This triggers Tristan’s transformation: he recognizes the Lion King’s path as evil, shattering his long-held philosophy. His Saint Graph inverts, forging him into the "Knight of Lamentation." Acknowledging his complicity in evil, he turns against the Lion King. In his final act, the inverted Tristan sacrifices himself to aid protagonists and Bedivere in escaping the fortress. He expresses desperate hope that Bedivere, embodying the true Round Table spirit he abandoned, can halt the Lion King and rectify Camelot’s failures where he could not. His last words lament his own unsalvageable nature.