Yu-Gi-Oh! GX episode 29: "Doomsday Duel, Part 1"
The Shadow Riders, known in Japan as the Seven Stars Assassins 「セブンスターズ刺客, Sebunsutāzu Shikaku」, serve as the main antagonists of the first season of Yu-Gi-Oh! GX, intent on resurrecting the Sacred Beasts. They are composed of 7 Duelists and their leader of varying origins and backgrounds who each have their own agendas.
Enlisted by the elderly Kagemaru in his quest to retrieve his lost youth, the Shadow Riders are a collection of elite duelists who work towards the goal of reviving the Sacred Beast Cards (三幻魔, Sangenma, Three Phantom Demons). Each of the members that Jaden and company face possess a Shadow Charm (闇のアイテム, Yami no Aitemu, Dark Item in the Japanese Version), similar to the Millennium Items in terms of supernatural power, but of unknown origin. These relics bestow upon their owners different abilities depending on the Shadow Rider in question.
In the past, Kagemaru was forced to seal the Sacred Beast Cards away behind the Spirit Gates underneath Duel Academy due to their inability to grant his wish at that time. In order to access their true abilities, he bestows upon Chancellor Sheppard the seven keys capable of unlocking the Spirit Gates and then pits his subordinates against the school's finest to create the strong dueling presence needed to resurrect the Sacred Beasts cards.
- The groups original name, The "Seven Stars" may be a reference to the Biblical Seven Stars in the Book of Revelation.