Obake

Bob Aken is a mysterious villain and former SFIT student in the world of San Fransokyo with a strange fascination towards Hiro, extending to the Big Hero 6 since before they officially decided on being superheroes. He has control over many other villains including Mr. Yama. Through Yama, he also worked with Momakase. In the episodes "Mini-Max" and "Countdown to Catastrophe", Obake was revealed to be Granville's student whom she allowed free rein in his research. This resulted in him suffering injuries caused by an explosion from his attempt of creating an energy amplifier, severely affecting his temporoparietal junction, the part of the brain responsible for morality, which greatly warped his sense of morality and is gradually worsening; despite being given awareness from Baymax, he refuses treatment, finding the condition "liberating". Out of this insanity and his obsessions, Obake masterminded various events in the first season from Globby stealing one of Lenore Shimamoto's paintings for her energy amplifier blueprint to pointlessly learning of Big Hero 6's identities through hacking Krei's personal files and Burger Noodle Boy's prediction algorithm. Obake finally reveals himself while acquiring the notes he needed from Shimamoto's journal, furthering his goals by help in Steamer's capture and acquiring a super magnet by subjecting the team to their fears. In the three-part season one finale "Countdown to Catastrophe", acquiring the power amplifier Hiro made while hijacking Baymax, Obake reveals his goal to recreate the Great Catastrophe and remake San Fransokyo in his image with Hiro as his apprentice. But the Big Hero 6 circumvent the disaster, with Obake resigning himself as his underwater base crumbles from the shockwave with his fate left ambiguous, only the evil chip he used to corrupt Baymax he kept in his final moments left alive, implying he could have somehow downloaded his consciousness inside of it.

Role in the series
Obake's chipped consciousness is retrieved by Dr. Cyborgus, a robot Mothron and leader of The Five Pariahs, hired by Nega-Xehanort to retrieve San Fransokyo's hidden Keyblade for construction of the X-Blade. Obake is granted the body of a powerful robot capable of adapting to anything, making him the perfect unstoppable bodyguard and assistant.