Mastermind is power hungry, and wishes to gain full domination of the planet as he did in the past. He has a British accent and prefers to dance (he dances like a sick moose). He also has a short temper, which results in his head being engulfed in green flames which are usually extinguished by emergency water sprinklers.
At first, Mastermind used to be a humanoid wizard with a pointy beard who used have an imperium that spanded 12 continents on a planet that had 7. After that he took the form of a levitating purple skull surrounded by green flames, which seriously impaired his abilities. Last, he took posession of Yang's body, by swapping brains with Yang. His mittens also seem to be sentient, but also serve as hands once required.
In his human form, Mastermind was able to cast lighting from his mittens. His skull form probably has less abilities, since Mastermind uses enchanted coupons to perform his possession ability. Through this, Mastermind is able to swap brains with the other who willingly signs the coupon. When Yang signed the coupon, he got a large sombrero in exchange for his body. After the possession, Mastermind is able to use all of Yang's abilities, with the exception of experiencing pain(due to all the feeling of pain being transfered to Yang while he was just a brain).