Caesar Clown, also known as "Master", is a former scientist of the Marine's research institute and a major antagonist in the "Punk Hazard" arc of One Piece. Known for his genius intellect in chemistry and weapons of mass destruction, Caesar often conducts unethical experiments, showing a sadistic enjoyment in the suffering he causes. He possesses the Gasu Gasu no Mi, a Logia-type Devil Fruit that allows him to create, control, and transform into gas at will. His actions make him a dangerous and unpredictable adversary to the Straw Hat Pirates.