Fall Cup Duel Project
The grand prize was the Field Spell Card "Golden Castle of Stromberg", which was developed for test purposes and never officially released. As there was only ever one copy, "Golden Castle of Stromberg" became sought after by many collectors. At some point, the influential Schroeder family was able to acquire the card. During the Grand Championship, Zigfried von Schroeder hacked into KaibaCorp's Duel Computer Limiter so that "Golden Castle of Stromberg" would be recognized as a legal card, and had said card modified so that when his brother Leon played it in his Duel with Yugi Muto, a computer virus would infect KaibaCorp's mainframe and delete all of the company's data in Duel Monsters, as part of Zigfried's plot to exact revenge on Seto Kaiba.