Yami Marik

Yami Marik is the evil side of Marik Ishtar, and one of the few characters more evil and sadistic than Yami Bakura.

The Anime
Yami Marik was created out of Marik's hatred and anger at the Pharaoh for having to be his tombkeeper. He took over Marik's body and imprisoned his father in the Shadow Realm, but was contained by Odion. Yami Marik did murder his father in the japanese version (he sent his father to the shadow realm in the dubbed version).

Battle City
When Odion was knocked out by the Winged Dragon of Ra, Yami Marik was able to reawaken within Marik, possessing his body and trapping him inside his mind. He proceeded to duel as Marik Ishtar in the tournament.

Yami Marik's duels were all twisted shadow duels. In the quarterfinals, he dueled Mai Valentine in the Shadow Realm, in which whenever a duelist lost a monster (to an attack by their enemy), someone would be erased from their memories. Unlike Mai, Yami Marik did not mind this at all, as there was no one in his mind worth remembering. He lost Strings and Arkana during the duel. Yami Marik defeated Mai and trapped her soul in the Shadow Realm.

Yami Bakura dueled Yami Marik, with Marik's spirit alongside him to regain his body. The two evil spirits dueled in the Shadow Realm, in which whenever a player lost life points, their body would vanish. Yami Marik won, and Yami Bakura was trapped in the Shadow Realm (though he escaped to Yugi's Millennium Puzzle).

Enter the Shadow Realm
The tournament was interrupted when Noah made the blimp land at a station where his virtual world was located in, and after Noah set the virtual world to explode, Yami Marik destroyed the control center so it could not be stopped.

Battle City continued from here, and a four-way duel between Yugi, Kaiba, Joey, and Yami Marik was held to decide who would face each other in the semifinals. Yami Marik and Joey both lost (as Joey intended), so they dueled in the semifinals. Yami Marik took their duel to the Shadow Realm, in which players would lose life energy as their monsters were destroyed. Just as Joey was about to win, he collapsed from the energy he lost, and Yami Marik won by default. However, Joey's soul did not go to the Shadow Realm.

Yami Marik dueled Yami Yugi in the final round, in which Marik and Yugi would disappear whenever they lost life points, either to be destroyed or trapped in the Shadow Realm. Eventually, his Winged Dragon of Ra was destroyed, and Marik and Yami Marik were switched around, making Yami Marik the victim. No longer evil, Marik decided to forfeit the match so the Pharaoh could fulfill his destiny. Yami Marik tried to convince him not to, but was unsuccessful, and as Marik lost the duel, Yami Marik was destroyed, and Mai released from the Shadow Realm.

Waking the Dragons
An apparition of Yami Marik appeared as a lost soul alongside Bandit Keith, Arkana, Seeker, the Paradox Brothers and Panik as Yami was trying to get to Yugi, whose soul was taken by the Orichalcos. It is unlikely that this was really him (as opposed to some sort of illusion), however, as neither Arkana, the Paradox Brothers, nor Bandit Keith were dead, in the Shadow Realm, or taken by the Orichalcos. It is possible, however, that they were all sent to the Sahdow Realm after failing their former masters, since Pegasus and Marik both had a Millenium Item, and thus had the power to banish souls to the Shadow Realm.