Willam, for a time, was mostly out of the game for Lyoko missions, often being kept safe under Yumi’s worry. But when balancing school work and Lyoko was getting to be much, William had to be brought in as a new member. But his time on the team didn't last long. Getting cocky and trying to take down the dreaded Scyphozoa, it proved too much as it grabbed him. Using its power, it put William under XANA’s control as a pawn. He dealt the final blow to the core of Lyoko. But he did not perish, but was put under Xana’s complete control as his general.
Originally, Willam had a silver outfit and a massive two handed sword that could also fire projectiles. But in Lyoko’s destruction, his outfit turned black with arm spikes and XANA’s mark on his chest. It could also be seen on his blade, with black vines on it with XANA’s mark on it as well. He even gained control over monsters, able to ride Manta’s and the ability to turn into super fast black smoke. His mission was simple, activate towers, lure Aelita in, and drop her into the Digital Sea. Eventually, after a long battle, William was eventually freed from XANA and continues his normal life as a student.