Tragoedia is the main antagonist of the Yu-Gi-Oh! GX manga. He was formerly a citizen of Kul Elna and survived the village's massacre, as he was not in the village when the massacre took place. This ultimately resulted in the creation of a powerful ka. He was sealed by several of the Pharaoh's priests, and reemerges in modern times by possessing the bodies of others, with his goal being the restoration of his body and revenge on the "ghosts" of the priests through the spirit cards.
Back in the times of ancient Egypt when Aknamkanon ruled, he was one of the citizens of the village of Kul Elna, who gained an upper position in the Pharaoh's entourage as a court astronomer. However, after learning about the massacre that decimated his village (ordered by Akhenaden so as to create the Millennium Items), his hatred and anger led to the creation of an extremely corrupted and powerful Ka, that being Tragoedia. While judged by the original priests who held the Millennium Rod and Millennium Scale, and by Akhenaden himself, the criminal was judged through the ba Winged Kuriboh, which was white at the time, but turned black after coming into contact with the malice inside the man's heart. Tragoedia attempted to kill the priests, and Winged Kuriboh absorbed the Feather of Ma'at. Tragoedia was sealed then, though his power was so great that he remained aware of himself even while sealed, and so his tablet was smashed and its remains buried in the royal tombs. Akhenaden and the other priests vowed to take the memory of what happened there to their graves, so as not to alarm the Pharaoh.
Three thousand years later the burial chamber in which Tragoedia lay sealed was opened by archeologists, and slowly began body-hopping, finding suitable hosts to further his needs. Ultimately he would end up in Mr. Phoenix's body and with his position as a card designer at I2 to create the Legendary Planets, its astronomy theme symbolizing his original characters occupation in the Pharaoh's courts. He would later come to possess the head of the American Duel Academy, with the intention of using someone of a high position to utilize many pawns. He would come to reveal that in his fathers absence, he had raised Edo to be his perfect pawn. It was also known that he adopted David Rabb as his son, because the boy had no known relatives.
He acted through MacKenzie, and was able to possess David, whom he sent to Duel Academy's main branch with Reggie MacKenzie in order to obtain the spirit card in which his heart was still sealed - "Winged Kuriboh". After Rabb's defeat at the hands of Chazz Princeton, Tragoedia uses Reggie as his main enforcer, but does not appear to have the same influence over her as she did over David, as she plots against him at the same time.
Principal Mackenzie journeys to the main branch of Duel Academy, and Tragoedia begins using James Crocodile Cook to continue the quest that Reggie had abandoned. Through his MacKenzie persona, he manipulated both Aster Phoenix and Adrian Gecko without need of possession, while using Jim, Jesse Anderson and Axel Brodie to gather energy through the Legendary Planets. Ultimately, he succeeds in his plot to regain his heart by possessing Atticus Rhodes and defeating Jaden Yuki. Using the gathered energy from the "Legendary Planets", he extracts his heart from "Winged Kuriboh" and becomes whole again, but not before discarding his minions. He faces Jaden and Chazz in a final Duel, but ultimately loses to their combined monster, "Ma'at". Tragoedia then finally abandons Principal MacKenzie, and muses that he could easily crush Jaden and Chazz like insects. Winged Kuriboh and Light and Darkness Dragon ultimately sacrifice themselves to seal away Tragoedia once and for all.
As an embodiment of wickedness and corruption, Tragoedia can possess people at will and use the power of darkness as a means to restrain, kill or plunge any duel into a dark counterpart of itself, a Shadow Game. He is however extremely weak against the powers of the "Light and Darkness Dragon", calling it the Feather of Ma'at, as when Chazz met Koyo Hibiki, Winged Kuriboh's spirit transferred the Feather of Ma'at it had absorbed in Egypt into Chazz's "Light and Darkness Dragon" card, thus giving it its spirit.
Tragoedia uses a Deck based around his ace monster "The Supremacy Sun", while supporting it with cards based around Egyptian Mythology. He uses this Deck whilst possessing Principal MacKenzie.