Atticus is able to counter this by removing "Red-Eyes Darkness Dragon" and its related cards from the Deck. Nightshroud then Duels against Atticus through Yusuke Fujiwara using a "Clear" Deck, reflecting his worldview.
After Fujiwara's defeat, Nightshroud uses a Darkness Deck while in his true form.
While possessing Fujiwara, Nightshroud plays a Clear Deck, which focuses on the use of his Field Spell "Clear World" to cripple his opponent's monsters while his own monsters, immune to its effects (since they have no Attribute while on the field), overwhelm the opposition with a combination of special effects and brute force. The Deck itself is a reflection of Nightshroud's beliefs: individuality brings suffering, while nullification relieves it.
In his true form, Nightshroud runs a Darkness Deck, focusing on the Field Spell of his namesake, "Darkness", and a long chain of Trap Cards supported by it, as, by activating his "Zero" and then his "Infinity" cards, every other Trap activates and gives Nightshroud a variety of effects to use. In addition, the monsters in this Deck interfere with aspects of the Duel, as well as let him ignore the negative drawbacks of his Field Spell, with his strongest being "Darkness Neosphere", which has the ability to control nearly the entire field.