Python Jack (パイソン＝ジャック, Paison Jakku) is a minor antagonist in the series.
He is an insane serial killer who kills just about anyone he meets just for fun. It is later revealed that he was not always like this, and used to be a regular O.P.T. who was called on by his village to try and activate a newly unearthed O-Part, Biraiya. When the attempt backfired, he got burned badly, and got extremely deformed. The rest of his village turned on him for his creepy and deformed look, causing his personality to become the way it is now. He is eventually 'eaten' by Lucifuge and is later seen floating in the limbo of another dimension which is Lucifuge's stomach.
He is wrapped up in bandages like a mummy who made his first appearance in the Rock Bird arc.