Jailer Beasts

The Four Demon Guards are the fiercest guardians of the Undersea Gaol, Impel Down, aside from the Warden Magellan. They appear to be under the command of Sadi-chan. This group consists of Minotaurus, Minorhinoceros, Minokoala, and Minozebra.

Appearance
The Four Demon Guards are gigantic bipedal animals that wear pants but no shirt, with the exception of Minorhinoceros, who wears overalls. In chapter 544, Crocodile reveals them to be "awakened" Zoan users. They each have runny noses and cutesy eyes (except Minozebra, who has a bored look). They all have comical and harmless appearances, despite their feared reputations. Like many of the important crews and groups in the series, Demon Guards all have animal themes:
 * Minotaurus: A giant bipedal cow with a spiked mace.
 * Minorhinoceros: A giant bipedal rhinoceros in overalls with two spiked maces.
 * Minokoala: A giant bipedal koala with spiked knuckles around its wrists.
 * Minozebra: A giant bipedal zebra with a spiked mace with a long shaft.

Personality
Despite their comical and harmless appearances, all four of them are ruthless creatures who brutalize the prisoners of Impel Down, making them the most feared creatures within its walls, second only to Magellan, making them worthy of being called "demons". Minorhinoceros is also bashful, while Minozebra is shy. This further shown in the anime, where Minorhinoceros was embarrassed to show himself and Minozebra hid behind Minokoala.

Despite their savage brutality, they are at least intelligent and subservient enough to understand and follow commands given by the human guards, shown where Buggy repeatedly told them they could not kill him by chopping him, but continue doing so. They also seem to fear Sadi-chan when she gets angry with them.

Abilities
The Four Demon Guards are the most feared creatures within the confines of Impel Down due to their great strength coupled with their blood lust and ruthlessness. Because they are "awakened" Zoan users, they are incredibly durable and recover quickly from injury. Despite this they are no match for some of the series' more powerful characters (namely Luffy, Jinbei and Crocodile), evident by the fact that all four of them were defeated all at once by only the first two in an instant.


 * Minotaurus: He has incredible speed and strength, which, combined with a giant mace he carries, makes him a lethal force to be dealt with.
 * Minorhinoceros: Wielding two spiked maces, its full abilities are not yet known. Presumably has incredible speed and strength
 * Minokoala: An armed fighter wearing spiked knuckles, its full abilities are not yet known. Presumably has incredible speed and strength
 * Minozebra: Using a mace with a long shaft, it threw a number of prisoners into the Pond of Blood, its full abilities are not yet known. Presumably has incredible speed and strength

Anime and Manga Differences
In the manga, the mace weapons that the Demon guards use are spiked. The reason for this is not explained. In the anime, they are changed to more rounded stubs. Also, the Demon Guards showed their personalities more in the anime, such as Minorhinoceros' bashful nature led to it being embarrassed while Minozebra hid behind Minokoala from shyness.

Trivia

 * They are the first Devil Fruit users where their true forms are never seen. In fact, nobody realized they were Devil Fruit users until Crocodile pointed it out.