Impel Down

Impel Down (インペル　ダウン), the Great Jail, is the World Government's maximum-security prison for the most dangerous criminals and pirates. Its name derives from the English verb 'impel', meaning to force. Some translations use the word Gaol which is an early Modern English spelling for jail.

It is located underwater in the middle of a Calm Belt. The only way to get there with the greatest of ease, one must use a water current accessible by going through the Gates of Justice located at either the Marine Headquarters or Enies Lobby. Also, the only way to safely get to the prison is to use one of the seastone lined Marine battleships as the entire place is surrounded by Sea Kings.

Because of its brutal nature and being renowned for being inescapable since Kinjishi, almost no person wishes to ever go there. However, there are people who choose to enter it willingly such as Luffy and Crocodile.

General Layout
Impel Down is a large submerged tower like structure that whose foundation is at the very bottom of the sea bed. Due to it being built within the Calm Belt, the entire structure is constantly surrounded by gigantic Sea King swimming alongside underneath the waves. Along with these beasts, the prison is guarded by a force of Marine battleships and crew greater than any Buster Call.

Within the dark confines of the prison are various cells and torture chambers that used for the prisoners. The torture chambers are used for all sorts of brutal unspeakable acts. Among these include continuous whipping, brutal beating to death, boiling cauldrons for burning and drowning, and spiked pits used for impaling.

The prison is carefully monitored all around by a Surveillance Den Den Mushi. Tiny versions of them are found in specific locations throughout Impel Down, whatever they see is transferred to a larger version that sends video feeds to a machine it's connected too, allowing the guards to view video screens. Each of the smaller versions has an alarm beeper connected to the shells.

Levels
When a prisoner arrives in Impel Down they are put in boiling water to disinfect and sterilize them. This is ritually referred to as "baptizing" them. While most have screamed in pain due to the extreme heat, only a few prisoners have been known to take the sterilization without flinching even one bit. These prisoners include Ace, Jinbei, and Crocodile. After being sterilized, they are then placed in one of the five known levels of Impel Down based on their crimes and strength. The more heinous or powerful a prisoner is, the lower the level they will be placed.

Along with various cells to keep inmates, each level possesses a unique form of torture. Because of these unspeakable acts being performed, each level is given the title of hell.

Level 1: Crimson Hell
The first level of Impel Down in which prisoners are kept in. While the level relatively is used for less wanted criminals, it contains a large forest of red trees. The leaves of the trees, known as Kenju (剣樹), are as sharp as blades while the grass on the floor, the Haribarisou (針グ草), is as spiky as needles. Here prisoners are forced to run through the forest while being chased by poisonous spiders and guards to experience all the pain from being cut from all directions. As consequence of prisoners being forced through this forest, it is soaked in blood. Deep within the forest is a hole that leads to level 2. For those who do not wish to live through the pain of being cut any longer, they were given the option of jumping down the hole to level 2, which rests an even more terrifying hell that nobody is willing to use.

Level 2: Wild Beast Hell
The second level of Impel Down in which prisoners are kept in. It contains various wild beasts of sorts. The beasts kept here include Puzzle Scorpions and Manticores. Puzzle Scorpions are large poisonous insects that can join together to become giant centipedes. Manticores are man-eating human faced lions that can devour everything from their prey including the bones. Their human faces allow them to speak however they can only imitate what they hear like parrots as they don't understand what they're actually speaking. The words they speak are mostly things they heard from the prisoners however, some things they say are completely out of place. Among these regular-sized beasts kept here are also two gigantic beasts, the Basilisk and the Sphinx.

The Basilisk is a gigantic snake born from a chicken. It is a feathered mutant that possesses both snake and chicken traits. It is extremely strong that it gave Luffy and Buggy a good chase until it was downed with one blow of Gear Third from Luffy. Though formidable, the Basilisk is not most powerful beast in the level.

Currently, due to both the Basilisk and the Sphinx being defeated, along with all the prison doors being unlocked, there is a mass riot in the level. The Sphinx is a gigantic human faced feathered lion. Significantly larger than the Basilisk and much more fearsome than the other beasts, it is considered the "boss" of the level and is charged with guarded the stairway that leads out of the level. It is so fearsome that the prisoners kept in the level, and even the other beasts hide from it. Like the Manticores, it is capable of imitated speech. It randomly says the names of types of noodles and apparently understands the concept of giving thanks before meals. It is such a strong beast that it is capable of breaking the floor beneath it if it hits it enough times.

With these various beasts, prisoners kept here are forced to be chased by them through the corridors of the level. Because of the fearsome danger, prisoners often either lose the will to go on, or refuse to escape even when their cells are unlocked.

Level 3: Starvation Hell
The third level of Impel Down in which prisoners are kept in. Most of the prisoners kept here are pirates who have a bounty of over 50,000,000. On this level, prisoners feel the heat rising up from Level 4 and are given precious little food and water to keep them in a near death state. And while the temperature here is nothing compared to the following level below, it is intense enough to cause overwhelming dryness, resulting in level 3's somewhat desert-like terrain. Mr. 2 Bon Kurei is kept here, despite his bounty is only 32,000,000. Recently, Luffy, Buggy, and Mr. 3 fell down to this level due to the Sphinx, who broke through the floor beneath them.

Level 4: Blazing Hell
The fourth level of Impel Down in which prisoners are kept. Prisoners from other levels are regularly tortured here, and there is an intense heat emitted from this level, which rises to the level above. For example, Buggy said he went through "Inferno torture" on this level. Magellan the warden of Impel Down stays here. Saldeath also mentions something about four demons who act as guards on this level.

Level 5
The fifth level of Impel Down in which prisoners are kept in. This is the level where criminals whose bounties are more than 100,000,000 are kept. Among the prisoners kept here are various pirates with deep grudges against Whitebeard. These prisoners include imprisoned giants alongside them. Ace and Jinbei are being kept here in a cell together. Although he had a former bounty less than a 100,000,000, Crocodile is also being kept here in a cell next to Ace's and Jimbei's cell. Here, prisoners seems to be regularly beaten by a club-wielding Minotaur.

Level 6
A mysterious level rumored by the prisoners to exist deeper than Level 5. It is said to keep criminals who are so powerful and dangerous that they have been erased by history by being kept here. However, it has been recently revealed in an map of Impel Down that there is a floor below level 5. What it is exactly, however, is unknown.

High Ranking Staff

 * Magellan: Warden, resides in Level 4, possesses the Doku Doku no Mi, only serves about four hours of service.
 * Hannyabal: Vice warden, ambitious person.
 * Saldeath: Chief Guard, commander of the Blue Gorillas.
 * Domino: Vice Guard.
 * Sadi-chan: Chief Guard, sadistic torturer.

Guards
Minotaurus: A Minotaur with a mace that beats the prisoners
 * Human guards: Either stationed in the monitor room or various other places. They vary in duties.
 * Blue Gorillas: Super strong and mindless gorillas with doubleheaded axe. Usually resides various levels.

Level 2 Beasts

 * Basilisk: Giant snake born from a chicken that shares traits of both creatures.
 * Manticores: Man-eating, human-faced lions that can eat their preys completely. Has the ability to talk but not understand what they are saying.
 * Puzzle Scorpions: Extremely poisonous creatures that can unite to form giant centipedes.
 * Sphinx: Boss of the level, extremely strong and guards the stairs. Also has the ability to talk but likewise with the manticores has no understanding of what what it is saying.
 * Hummingbirds: Wild beasts also found in Level 2. Only one has been shown.

Current known prisoners

 * Sir Crocodile (Mr. 0) (Life sentence) (Level 5)
 * Daz Bones (Mr. 1) (Life sentence)
 * Mr. 2 Bon Kurei (Life sentence) (Level 3) (Released from cell, currently with Luffy.)
 * Mr. 3 (Life sentence) (Level 2) (Released from cell by Buggy. Now teamed up Buggy.)
 * Portgas D. Ace (Death penalty in less than 33 hours) (Level 5)
 * Jinbei (Temporarily sentenced) (Level 5)
 * 500 pirates captured by Admiral Kizaru (Awaiting transfer)
 * Buggy the Clown (Level 1) (Vanished from cell, later teamed up with Luffy. Currently teamed up with Mr. 3.)

Crocodile and Mr. 1 were imprisoned in a Marine base, but were transferred to Impel Down after most of the captured Baroque Works members escaped (Crocodile and Mr. 1 chose to stay behind). Bon Kurei and Mr. 3 were captured by Hina, and presumably transferred to Impel Down for reasons similar to Crocodile and Mr. 1's transfers.

Defeating Portgas D. Ace led to Blackbeard becoming a Shichibukai, and Ace being sent to Impel Down. Ace is currently sentenced to public execution.

Jinbei has caused a wild outburst during his summons in the Marine HQ, and is sent to Impel Down until he is calmed, but he shows no sign in folding.

During the Sabaody Archipelago incident, Kizaru captured 500 pirates, and all of them are currently being transferred into Impel Down.

Buggy the Clown was transferred here after being captured after leaving the island he mistook for Treasure Island. Buggy managed to escape his cage in Impel Down, but it is unknown whether his acquaintance with Ace has any effect on his recent capture at Impel Down. With Luffy currently breaking in Impel Down to rescue Ace, he has teamed up with Buggy to get there, and fight off any guards that come on their way.

Trivia

 * Impel Down seems to be heavily based on how Hell is described in Dante Alighieri's Divine Comedy. Both are level-based, "inescapable" prisons with unique forms of punishment per level, and the lower one traverses, the worse the punishments become. Consequently, Luffy's journey to the fifth level of Impel Down can be likened to Dante's descent.
 * Each of the high ranking staff members seems to have a devil theme in their dress codes, a reflection to how each level of Impel Down is called Hell.
 * The Basilisk featured in Impel Down is based on a common mistake. Often depictions of the Basilisk show a "chicken-like" snake creature, but such a creature is actually known as a Cockatrice, as the legends are commonly mixed up.
 * According to Sengoku, only one prisoner has ever escaped from Impel Down; The flying pirate Kinjishi escaped 20 years prior to the present storyline. However, Sengoku blames the escape on the Marines' mistakes. Since then, no one has escaped, let alone infiltrated, Impel Down before Luffy.