Magellan is a towering, demonic-looking man who served as the Chief Warden of the great underwater prison Impel Down, and following a catastrophic failure, was demoted to the position of Vice Warden. His appearance is as formidable as his reputation, featuring a face resembling a mandrill with sharp teeth, a thick beard, and horns atop his head that can be detached and used as weapons. He typically wears a black suit with a red shirt, complete with bat-wing ornaments on his back, and after the two-year timeskip, his body bears large scars and broken horns from the near-fatal injuries he sustained during the prison break.

Magellan possesses a personality marked by a stark contrast between his professional ruthlessness and his personal quirks. He is deeply dedicated to his role, taking immense pride in Impel Down’s reputation as an impenetrable fortress. He is merciless towards criminals who challenge his authority or attempt to escape, having the permission to execute any prisoner on the spot and showing no hesitation in doing so with his deadly poisons. Despite this cruelty, he is not a sadist; he imprisoned his own head jailer, Shiryu, for killing prisoners for entertainment, demonstrating a strict adherence to his own code of justice. His most notable peculiarity is his chronic and severe diarrhea, a direct result of his habit of eating poison-laden food. Because his Devil Fruit makes him immune to the poison, he consumes it for flavor, but his body still reacts by causing him to spend roughly ten hours a day in the bathroom. Coupled with eight hours of required sleep, Magellan is only able to perform his duties for about four hours each day. He also has moments of being easily flustered, such as when he fell under the charm of the Pirate Empress Boa Hancock.

Magellan’s primary motivation throughout the story is to protect the integrity of Impel Down at all costs. He views any infiltration, escape, or insult to the prison as a personal affront. His role in the overall narrative is that of the primary antagonist during the Impel Down Arc, where he stands as the greatest obstacle to Monkey D. Luffy’s mission to rescue his brother, Portgas D. Ace. He is the ultimate authority within the prison, commanding a vast army of guards and blugori, and is considered its most powerful and reliable asset, a sentiment shared even by prisoners like Crocodile and Jinbe.

His key relationships are defined by his position. He has a complex dynamic with his ambitious subordinate Hannyabal, who constantly schemes to usurp him. While Magellan often responds to Hannyabal’s insubordination with a blast of poison gas, he also genuinely respects him, acknowledging that Hannyabal is the only man worthy of succeeding him as warden. In contrast, his relationship with the former head jailer Shiryu is one of utter contempt and betrayal. Magellan imprisoned Shiryu for his atrocities, but in a moment of desperation during the prison crisis, he reluctantly released him to help fend off the Blackbeard Pirates. This decision proved catastrophic, as Shiryu immediately betrayed the prison, massacred his fellow guards, and joined the invaders. Magellan also holds a deep-seated grudge against Monkey D. Luffy, whose successful infiltration and subsequent mass breakout were a direct humiliation that shattered the prison’s perfect record.

Magellan undergoes significant development through his failure. Initially, he is an overwhelming force of authority who effortlessly defeats Luffy and the Blackbeard Pirates, confident in his absolute power. However, the combined chaos of Luffy’s escape, Blackbeard’s invasion, and Shiryu’s betrayal leaves him defeated and near death. His pride is so wounded that upon regaining consciousness, he attempts to commit suicide to take responsibility for the incident. Though he survives, his failure leads to his official demotion from Chief Warden to Vice Warden, a humbling fall from grace.

Magellan’s notable abilities are entirely centered on the Doku Doku no Mi, a Paramecia-type Devil Fruit that allows him to generate, control, and excrete every type of poison imaginable from his body. He is completely immune to all toxins, which has allowed him to develop a wide array of lethal techniques. His standard attack involves releasing large streams of corrosive liquid poison that can melt flesh and bone. His signature technique, Hydra, shapes this poison into a massive, three-headed dragon that can pursue enemies and delivers a paralyzing, excruciatingly painful death to anyone it touches. He can also breathe out a poisonous gas that robs victims of their senses and strength, or spit bubbles of poison gas that act as a potent tear agent. His ultimate technique, Venom Demon Hell's Judgment, generates an enormous, crimson, skeletal giant made of a specially formulated poison so potent that it corrodes even inorganic materials and, as Magellan himself claims, has the power to destroy all of Impel Down. The only known natural weakness to his poisons is wax, which can provide temporary, limited protection.