Jack is an All-Star of the Beasts Pirates as one of Kaidou's three closest confidants, and the captain of the Mammoth. He was formerly considered to be the ruler of the region of Kuri in Wano Country. He is also a giant grouper fish-man. He is a giant grouper fish-man of massive stature. Unlike the majority of fish-men, his pale skin is identical to that of a human, making it easy to mistake him for one. He wears a metallic jaw mask and has a pair of horns on each side of his head.