
Within the dub of one episode of Yu-Gi-Oh! 5D's, it is mentioned that the Crimson Dragon has ties to the Shadow Realm. For some reason the Crunchyroll subtitles call the World of Darkness in the GX and Duel Monsters subs as the Shadow Realm. However, he lost to her and was dragged back there himself. He Dueled Alexis Rhodes, one of the holders of the Spirit Keys, intending to defeat her and drag her to the World of Darkness, just as her brother previously had been. Here, he met Kagemaru, who gave him his Shadow Charm mask, letting him return to Earth as one of the Shadow Riders. In the Japanese version of Yu-Gi-Oh! GX, Titan mentions that he was taken to the World of Darkness after losing to Jaden. In the final manga arc, it is also mentioned by the High Priest of Darkness that should one die in the Ultimate Shadow Game, they would not be sent to the afterlife when they die but to "a void of eternal darkness", reminiscent of descriptions of the Shadow Realm. However, in the dub, the term "shadow realm" is used interchangeably for both the original Japanese equivalent and the dub exclusive place. This was where the soul of Solomon Muto was placed after being absorbed into a " Soul Prison" card by Maximillion Pegasus. However, the concept is based on an occasionally mentioned place called the World of Darkness ( 闇 ( やみ ) の 世界 ( せかい ) Yami no Sekai). The Shadow Realm as presented in the English language version of the anime does not exist in the Yu-Gi-Oh! manga and the Japanese version of the anime. 5 Duels that took place in the Shadow Realm.The concept is also mentioned in the dubs of the Yu-Gi-Oh! GX anime and the Yu-Gi-Oh! 5D's anime. In Joey Wheeler and Yami Marik's Duel, Joey would have won if he hadn't collapsed after the attack of " The Winged Dragon of Ra" took away the rest of his stamina. In Yugi Muto and Pegasus's final Duel, Yami Yugi had to take over for the large portion because of the strain it had caused Yugi. The more monsters, the more energy it seems to require. When wagering a Duel in the Shadow Realm, Summoning and maintaining a monster requires energy.

It was this dark dimension (so named by Maximillion Pegasus) that formed the basis for the Shadow Realm in the English version. Shadow Games were depicted as occurring in another dimension which was also called the Shadow Realm. If a death or serious injury would occur in the Japanese version, the dub would censor it by having the victim be sent to the Shadow Realm instead hence, the Shadow Realm is regarded as a euphemism for death and other disastrous events used for the dub.
REDDIT CYBER SHADOW SERIES
It was designed by 4Kids Entertainment for the dubbed version of the Yu-Gi-Oh! second series anime. The Shadow Realm is alleged to be a place of suffering where people could be sent to.
