Nightshroud is an evil spirit as well as the true final antagonist of Season 16. He first appears when Goku tries to convince Bowser and Samus Aran not to give up hope. Nightshroud assumes the form of Atticus Rhodes, and then brainwashes Samus. Nightshroud and Zombie Reed then reveal to Goku that he is in Gigadark Bowser's mind, meaning Nightshroud is behind everything. Nightshroud then initiates the invasion of Gundalia by summoning Malefic monsters and taunts Goku about his inability to do anything. After the de-fusion of Gigadark Bowser, Nightshroud challenges Naruto Uzumaki, Jaden Yuki, and Zelda to a final showdown with the fate of the universe on the line. Ultimately, Nightshroud is defeated by the combined power of the newly evolved Drago and Armityle the Chaos Phantom. However, Nightshroud survives by possessing Samus as his new host. Nightshroud serves as the main antagonist in the first half of Season 17. At the start of Season 17, Nightshroud is seen on a motorcycle and almost runs over Ganondorf. After exchanging dialouge, the two decide to team up. After Ganondorf leaves upon learning of the intergalactic Duel Monsters tournament, Nightshroud possesses Seto Kaiba, who he uses to duel Yugi Muto and manages to possess Tea Gardner and Tristan Taylor as well. Later, Nightshroud duels Zane Truesdale through Tristan's body and wins by preventing Zane from defusing Cyber End Dragon, which he fused with Power Bond. Nightshroud then gives Ganondorf Obelisk the Tormentor, which he stole from Yugi along with The Winged Dragon of Ra. Later, Nightshroud duels Zane and Naruto through Samus and Tea Gardner, but is defeated and abandons Samus' body. Nightshroud then proceeds to use Kaiba as his main enforcer. Nightshroud returns later on to dispose of Ganondorf for his treason. Nightshroud then makes a similar deal with Yami Bakura, and later arrives on Gundalia during the siege, and is exorcised from Kaiba by Blue-Eyes White Dragon. Nightshroud is ultimately defeated for good when Samus vaporizes him, but his energy is absorbed by Yami Bakura. Nightshroud is revived when Yami Bakura uses De-Fusion along with his powers to split them apart in order to raise the stakes. Nightshroud would assist Yami Bakura during the Mind Maze Arc, but for some reason he vanished during the final battle. Nightshroud returns in Season 19, and it appears Yami Bakura still has some of his power. Nightshroud is later betrayed by Yami Bakura, and is reabsorbed. In Season 20, Nightshroud is revived when Bowser hits Yami Bakura so hard in the gut, that Yami Bakura is forced to regurgitate Nightshroud. During The Keys of Smash Arc, Nightshroud is forced to work with Yami Bakura again in order to gain the mysterious key the heroes acquired.
Nightshroud considers himself a god, as he wants to destroy the universe in order to remake it in his own image, where everyone follows his beliefs. Nightshroud also considers anyone who is fused with a spirit as filth that doesn't deserve to live in his new world. In Season 19, Nightshroud is much more vicious, as he wanted to end human suffering and the zombies beat him to it.