Sir Clavius (Clavius for short) (voiced by Jake Williamson) is a wicked magician and the main antagonist of Jaden's Adventures of The Swan Princess II. He was Sir Rothbart's former friend and partner. They both conquered the Forbidden Arts together until Rothbart took all the power for himself and drove Clavius underground. With Rothbart gone, Clavius planned to take the Forbidden Arts himself and destroy Derek. He kidnapped Queen Uberta (only to get annoyed by her talking) so that Derek would be out of the castle to rescue her. Clavius was able to sneak in and take the Forbidden Arts from a magic crystal ball, and challenged Derek to a fight. Clavius met his demise after the crystal ball was destroyed and his hideout exploded, taking his life too.