Trueman, also known as Mr. T, is a mysterious character that appears in the fourth season of Yu-Gi-Oh! GX.
As the powerful and mysterious "Messenger of Darkness" who vows to destroy those who try to figure out his agenda, Trueman serves as the primary antagonist of the fourth season. However, it is later revealed that he is the emissary of Nightshroud, the true mastermind behind the vicious siege.
Trueman, at one point, stated that he has no real name, but he chose the name "Trueman" because he claims he always speaks the truth (He does tend to use deceit and manipulation numerous times in non-verbal ways, however as he uses illusions to prey on victims.).
Trueman initially appears to dispose of Honest, a Duel Spirit who disguised himself as a long-missing Obelisk Blue student, Yusuke Fujiwara, only to be stopped by Jaden Yuki. Recognizing Jaden as a threat, Trueman attempts to destroy Jaden, only to be thwarted every time and retreats, promising to return. Trueman proves a difficult opponent for Jaden each time they Duel. In the first Duel Jaden won fairly easily but came very close to losing the second. Before their third rematch multiple Trueman(s) appear and they assimilate together to dispatch Jaden, considering him as a threat to their agenda. Jaden nearly loses this one, but manages to win using the card "Honest".
He later revives his machination and initiates a vicious assault on Duel Academy and Domino City, absorbing people into the World of Darkness by materializing through the cards of Duelists who have felt negative emotions and assuming their form, but not before eliminating the original. Additionally, when he does this, everyone who knew the person forgets they ever existed. Among the victims were Taigo Sorano, Axel Brodie, Sartorius, Sarina, Tyranno Hassleberry, and almost the entire population of Domino City and the students of Duel Academy. Names from a list of his victims, including many characters from the first series anime and manga, all disappear from the list leaving only Seto Kaiba's name behind.
To defeat Axel Brodie, Trueman copied the Deck and appearance of Brodie's father and exploits Brodie's negative emotions relating to an incident that nearly killed both of his parents. Many copies of Brodie later attempt to stop Jaden Yuki's escape from Domino City, but Jaden escapes them. However many copies of Jaden then try to stop Jaden, but he is rescuedd by Sartorius.
After defeating Taigo Sorano, Trueman begins to imitate both Sorano's Deck and appearance, enabling him to blend in with the other students of Duel Academy before finding his next victim. Each individual Trueman clone was capable of doing this, and so each of them would seek out students to defeat, among them Tyranno Hassleberry and Syrus Truesdale. He later assumes his true form once more and defeats Chazz Princeton and Alexis Rhodes.
Trueman has shown numerous abilities during the season, the most notable is being able to manifest from cards tainted with darkness. He can shapeshift into different people and copy their Decks. When he Duels against a particular person he takes appearances of either families, friends, or classmates that has related to that person in an attempt to psychologically weaken them.
He has shown the ability the teleport, manipulate matter, as well as the ability to create clones of himself.
Trueman plays an Archetype Deck, based around using the effect of "Dark Archetype" to Summon a variety of powerful monsters. Because he can manifest himself through any bunch of cards, for the most part, his Deck varies. As part of his darkness theme, most of his key monsters are of the DARKAttribute. Trueman's Deck also evolves each time he loses a Duel, as he has an improved Deck in the next Duel. He has displayed the ability to copy any Duelist's appearance and Deck, as long as the memory of the Deck exists. After his third loss to Jaden, he defeats Taigo Sorano and uses both his Deck and appearance to blend in with the rest of Duel Academy. He uses Sorano's Deck to defeat much of the student body, including Syrus Truesdale and Tyranno Hassleberry. With most of the students pulled into the World of Darkness, he reverts to his own Deck and defeats the remainder of the students, including Chazz Princeton and Alexis Rhodes. This leaves only Jaden Yuki and Jesse Anderson unaffected. Although he also copied both Axel's and Jaden's Deck, as taking their appearance, he didn't use them since Jaden succeeded to escape from him.