Trueman's main deck is an Archetype Deck, based around using the effect of "Dark Archetype" to quickly Summon a variety of powerful monsters. Because Trueman can manifest through any bunch of cards, his Deck features an enormous amount of variety. Running "Dark Archetype" helps to ensure his deck maintains a degree of consistency, even if it means taking heavy damage early in the game. Also, 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 (and usually more homogeneous) Deck in his next appearance. Trueman's Archetype Deck features three major stages during Trueman's duels with Jaden.
Trueman also has the ability to copy any Duelist's appearance and Deck, as long as public memory of the Deck exists. After his third loss to Jaden, he defeats Taigo Sorano and mimics both his Horus Lockdown Deck and appearance to blend in with the rest of Duel Academy. He uses Sorano's Deck to defeat most of the remaining student body, including Syrus Truesdale and Tyranno Hassleberry. With a majority of the students pulled into the World of Darkness (and thus memory of Sorano gone), Trueman reverted back to his own Deck to defeat the remaining students, including Chazz Princeton and Alexis Rhodes.
Trueman's crusade ultimately left only Jaden Yuki and Jesse Anderson unaffected. Trueman presumably also copied both Axel's and Jaden's Deck, as well as their appearance, but never used them since Jaden succeeded in escaping from him.