Magellan's biggest quirk is his severe diarrhea brought upon by his frequent consumption of poisoned food. His Devil Fruit power gives him immunity from actually being poisoned, but it doesn't spare him from diarrhea. As a result, he spends approximately ten hours each day in the bathroom relieving himself and 8 hours sleeping. It has been hinted that he is actually agoraphobic and enjoys dark, enclosed spaces.
Though he only performs roughly four hours of duty per day as Warden of Impel Down, he still takes his role quite seriously and does not tolerate the prisoners' bad behavior. As he has permission to execute any one of them he sees fit, he shows no hesitation to drench them in his Hydra's lethal poison. Magellan also takes great pride in keeping Impel Down's reputation of being impenetrable and inescapable, and felt personally insulted when Luffy became the first to besmirch that record.
Magellan seems to find it amusing whenever someone he doesn't particularly like gets poisoned or suffocated by his powers, evident when he was seen chuckling at Hannyabal after he sighed a poisonous mist at the latter's direction. While he also does not tolerate Hannyabal's "poisonous" (the actual term used is punned with the word "distant") comments he himself is prone to use them against himself. His ruthlessness applies not only to the prisoners, but also to his own men, as seen berating a guard who was accidentally poisoned by his Hydra. He will also not tolerate any of his own men who abuse their power, as he dismissed Shiryuu for killing prisoners for fun and had him jailed in Level 6. Despite the silly aspects of his personality, he is an extremely serious combatant, speaking little and never toying with his opponent.
Despite his ruthlessness and seriousness, Magellan was one of the many to fall for Boa Hancock's beauty, and neglected to hear the report of Luffy's intrusion when she requested to see Ace immediately, being completely head-over-heels over her.
He and Hannyabal are often at conflict with each other over Hannyabal's ambitiousness. Often Hannyabal will scold Magellan's behavior as he displays poor qualities as a warden overall, such as falling head over heels for Hancock and her charms. His actions will often invoke Magellan to send poisonous gas in Hannyabal's direction. Out of all his subordinates, Hannyabal is the one most likely to be the target of Magellan's poison. However, despite these conflicts, Magellan recognizes Hannayabal as the only man who would actually be worthy of taking over his place as Chief Warden.
Magellan seems to care very little to none for the well beings of his subordinates, especially when it comes to serving his duties as the warden of the place. He shows his ruthlessness by using his poisonous breath to put his subordinates into place, and drench them in the corrosive Hydra when they are in his way of battle, without as much as an apology.
Shiryuu, who killed many prisoners for fun, had earned Magellan's fury. Seeing that Impel Down is in its greatest hour of need, Magellan was willing to suspend Shiryuu's death sentence and reluctantly enlisted his assistance. However, this proved to be a mistake, as Shiryuu betrayed the prison, murdering his fellow guards and joining the Blackbeard Pirates.
He has permission to kill any criminal within the walls of Impel Down. He cares little for them and will willingly use extreme measures against them. His tolerance for prisoners runs extremely low. When pushed to react, he covers them in poison and leaves them with no cure. In turn, while most prisoners badmouth Magellan in his presence, they also fear him for his ruthlessness, and in particular, his Hydra technique.
Regardless, Magellan does not abuse his privilege of killing prisoners, and discourages his subordinates from doing so. He jailed Shiryuu and sentenced him to death for killing prisoners for fun.
Magellan holds a particular grudge against Monkey D. Luffy, the first man to ever break into Impel Down which is not only a tarnish to the Great Jail's perfect record since Kinjishi, but also a personal insult to himself as the Chief Warden. This hatred only intensified when Luffy led a large amount of prisoners on an attempted mass-breakout, causing the prison to face one of its greatest crises. Magellan swore that he would not allow Luffy to rescue Ace, nor let him step outside of the prison. Unfortunately, this vow was not kept, as Luffy successfully led a mass-breakout army out of the prison, leading Magellan to suffer the ultimate humiliation. To this end, Magellan took his revenge on the prisoner who stayed behind to help Luffy's escape, Mr. 2 Bon Kurei.
As the warden of Impel Down, Magellan has full control of the prison. However, because of his constant diarrhea, he spends most of his time in the bathroom. Adding to the fact that he sleeps approximately eight hours per day (And discounting meal times and breaks), he only works for approximately four hours per day doing his job.
Nonetheless, he has both the authority and the ability to execute any of the prisoners within Impel Down as he sees fit.
Magellan also seems to have great resilience, as he took one of Monkey D. Luffy's Gear Second attacks straight on and managed to stand back up to continue fighting. He has also been on the receiving end of multiple shots of cannon fire without any resulting injuries, and has easily blocked a wax-covered Gomu Gomu no Stamp with one arm. Only Emporio Ivankov managed to wound Magellan's forehead after a short duel.