Siegfried von Schroider (ジークフリード・フォン・シュレイダー, Jīkufurīdo fon Shureidā), also known as Zigfried von Schroeder in the English dub, is an anime-only character who appears in the KC Grand Prix arc as an antagonist. He uses the alias Sieg Lloyd (Zigfried Lloyd in the dub) to enter the tournament.
Siegfried is the CEO of a European-based company that specializes in the gaming industry and holographic technology. Because they cater to the same market, it is in competition with Kaiba Corporation, and Siegfried sees Seto Kaiba, KaibaCorp's CEO, as a personal rival. This rivalry turns to contempt when Kaiba succeeds in making a business deal with Pegasus J. Crawford, an opportunity that Siegfried wanted for his company, and he resolves to one day take his revenge against Kaiba.
After the events of the Doma arc, KaibaCorp is left weakened, and Siegfried sees this as his opportunity to destroy the company. He enters a tournament that is being hosted by KaibaCorp under a fake name and wins his way to the finals, defeating Katsuya Jounouchi along the way, where he is set to dueling his younger brother Leonhart von Schroider, who also entered the tournament under an alias. The match is halted, however, by Kaiba, who announces that Siegfried is disqualified and that Leonhart has won by default.
Siegfried and Kaiba proceed to duel under the pretense of appeasing the audience. Kaiba is the victor, but Siegfried continues with his plans for revenge by giving a virus-infected card to Leonhart, who is scheduled to duel against Yuugi Mutou next. Once played, the card (Golden Castle of Stromberg) will infect KaibaCorp's computer systems and cause them to crash. Though Leonhart does play the card, he realizes his brother has been lying to him, and with Dark Yuugi's help the card is destroyed. Kaiba then neutralizes the virus, and Siegfried accepts that his revenge has failed. He then apologizes to his brother for manipulating him, showing that he truly does care about him, and sets aside his resentment for Kaiba.
Siegfried's deck utilizes cards that are named after the German operas of Der Ring des Nibelungen. Siegfried's name is also derived from these operas.