Ghost Kaiba

The Death Imitator/Mimic of Doom (his English Anime name was not revealed until Yu-Gi-Oh! Reshef of Destruction) was one of Pegasus' hired Player Killers (Eliminators in the English anime dub version). He was either an extremely talented master of disguise or, more likely, a shapeshifter. He even seemed capable of altering his own body weight. His true form was that of an ugly, obese clown who dressed up as Kaiba to duel Yugi. He claimed that Kaiba was dead and that he was Kaiba's ghost back for revenge (in the dub, he said he was Kaiba's evil half that Yugi sent to the Shadow Realm). The Imitator had taken Kaiba's deck and used it in the duel. Yugi defeated him and used the Millennium Puzzle's power to send the Death Imitator into a coma (in the dub, he drove all evil from the Imitator). In the manga, the Imitator controlled a dummy version of Seto Kaiba that was channeling the real Kaiba. When Yugi won, he made the dummy come to life and beat up the Imitator.

Dueling Cards
The Mimic of Doom used Kaiba's Deck, wich was stolen by Pegasus' henchmen.

Monster Cards

 * Blue-Eyes White Dragon
 * Hitotsu-Me Giant
 * Grappler
 * Mystic Horseman

Trap Cards

 * Defense Paralysis (TCG & OCG Equivalent: Stop Defense)
 * Negate Attack