Sir Crocodile is the former president of the mysterious crime syndicate Baroque Works. He was originally introduced as a Shichibukai but was later stripped of his title after attempting to take control of the desert kingdom Alabasta. Thanks to Luffy, he managed to escape from Impel Down and went to Marineford to participate in the war; after that, he and his subordinate Daz Bones decided to head out to the New World.
Crocodile ate the Logia Devil Fruit, Suna Suna no Mi, allowing him to become, generate, and manipulate sand. He has mastered his ability to the point of perfection and can turn into sand reflexively if attacked; this became especially obvious after Doflamingo cut his head off while he was distracted.