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Impel Down, also known as the Underwater Prison (海底監獄 Kaitei Kangoku?) or the Great Prison (大監獄 Dai Kangoku?), is a government-controlled stronghold in Paradise together with Marine Headquarters and Enies Lobby. It is the World Government's maximum-security prison for the most dangerous criminals and pirates. It is located underwater in the middle of the Calm Belt.
Impel Down is the main setting of the Impel Down Arc.
Impel Down is a large submerged tower-like structure 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 Kings swimming below the water. Along with these beasts, the prison is guarded by a force of Marine battleships.
Within the dark confines of the prison are various cells and torture chambers that are used for the prisoners. The cells are all made from seastone to keep those with Devil Fruit powers from escaping. 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 monitors connected to it, allowing the guards to keep surveillance. Each of the smaller versions has an alarm beeper connected to the shells. The large Surveillance Den Den Mushi is kept in a monitor room somewhere within the fortress.
There is also what appears to be a medical laboratory stationed somewhere within the great jail, with doctors and a variety of medical equipment for immediate treatments of anyone within the prison, both prisoner and staff alike. However, the doctors seem to have a limit, as they cannot produce a cure for an accumulation of various poisons.
- †: the character is deceased.
- *: the character's status is unknown. Hovering the symbol may give further details.
- ≠: the character is non-canon.
- ‡: the character is no longer part of this group. Hovering the symbol may give further details.
Impel Down StaffEdit
High Ranking StaffEdit
|Hannyabal||Chief Warden; Former Vice Warden (副署長 Fuku Shochō?)||
|Magellan||Vice Warden; Former Chief Warden (監獄署長 Kangoku Shochō?)|
|Saldeath||Chief Guard (牢番長 Rōban Chō?)||
|Sadi||Chief Guard (獄卒長 Gokusotsu Chō?)||
|Shiryu||Former Head Jailer (看守長 Kanshu Chō?)||
|Domino||Head Jailer; Former Vice Head Jailer (副看守長 Fuku Kanshu Chō?)||
Guards and BeastsEdit
|Human Guards||Various Levels||
|Blue Gorillas||Level 1||
|Puzzle Scorpions||Level 2||
|Giant Rat||Level 2||
|Wolf Unit||Level 5||
|Giant-Mouth Hippo||Level 2||
|Giant Praying Mantis||Level 2||
|Name||Crimes||Sentence and Status|
|Buggy||Former; Piracy: captain of the Buggy Pirates||
|Jean Goen||Unknown reason.||
|Galdino||Former; Membership in Baroque Works.||
|An Zengaiina||Unknown reason.||
|Bentham||Former; Membership in Baroque Works.||
|Daz Bonez||Former; Membership in Baroque Works.||
|Monkey D. Luffy||Former; Infiltrating Impel Down in attempt to break Portgas D. Ace out of prison.||
|Emporio Ivankov||Former; High Officer of the Revolutionary Army.||
|Inazuma||Former; Membership in the Revolutionary Army.||
|Roche Tomson||Unknown reason.||
|George Black||Unknown reason.||
|Shiki||Escaped; Piracy: captain of the Golden Lion Pirates||
|Portgas D. Ace|
|Jinbe||Former; Causing an uproar at Marine Headquarters, and refusing to fight on behalf of the World Government.||
|Shiryu||Unacceptable abuse of privilege: killing prisoners for personal reasons.||
|Catarina Devon||Former; World's worst female prisoner in the entire pirate age.||
|Sanjuan Wolf||Former; Unknown reason.||
|Vasco Shot||Former; Unknown reason.||
|Avalo Pizarro||Former; Unknown reason.||
|Arlong||Piracy, membership in the Sun Pirates. Attempted murder of Marines and humans.||
|Pankuta Dakeyan||Unknown reason.||
|Shuzo||Several attacks to pirates and marines, membership in the Neo Marines.||
|Kairo Kureyo||Unknown reason.||
|Dobby Ibadonbo||Unknown reason.||
|Doha Ittanka II||Unknown reason.||
A prisoner's assigned level is usually determined by the bounty value on his or her head. Exceptions can be made however, such as Crocodile whose bounty was removed a long time ago and Bentham, when the Government acknowledges their strength is obviously superior to their bounties.
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. With each descending level, the tortures worsen.
Level 1: Crimson HellEdit
Crimson Hell (紅蓮地獄 Guren Jigoku?) is the first level of Impel Down in which prisoners are kept. The level houses the least-infamous prisoners and contains a large forest of red trees. The leaves of the trees, known as Kenju (剣樹 bladed tree?), are as sharp as blades, while the grass on the floor, the Haribarisō (針々草 needle grass?), 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 a 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 contains an even more terrifying hell that nobody is willing to risk. The security here seems to be somewhat lax, as a prisoner has managed to sneak a Black Den Den Mushi into his cell, eavesdropping on what is happening around the fortress.
Buggy was kept here prior to his escape due to the guards not knowing he was a Devil Fruit user, much less one whose power rendered him completely impervious to this type of torture.
Level 2: Wild Beast HellEdit
Wild Beast Hell (猛獣地獄 Mōjū Jigoku?) is the second level of Impel Down in which prisoners are kept. Buggy commented that every prisoner that was imprisoned on Level 2 and escaped alongside him holds a bounty higher than his own (15,000,000). 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 will 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 do not understand what they are actually speaking. The words they speak are mostly things they heard from the prisoners so some of the things that 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 and 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 the most powerful beast in the level. It is considered to be the "second-in-command".
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 guarding 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.
Galdino was kept here prior to being set free by Luffy and Buggy. After both the Basilisk and the Sphinx were defeated, and along with all the prison doors being unlocked, there was a mass riot in the level caused by Luffy and his companions. The riot however was quelled down by Saldeath and his Blue Gorillas. There was a second riot that occurred shortly after the previous riot but was quelled after Magellan apparently decimated almost all the prisoners on the level and blocked all the entrances and exits. However, as Magellan became occupied with Luffy's breakout army, the rioters of Level 2 once again became active.
Level 3: Starvation HellEdit
Starvation Hell (飢餓地獄 Kiga Jigoku?) is the third level of Impel Down in which prisoners are kept. Most of the prisoners kept here are pirates who have a bounty of 50,000,000 or higher. 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. They are reduced to the point where, by merely looking at them, one cannot tell that they were ever once frightening criminals. Also while the temperature here is nothing compared to level below, it is intense enough to cause overwhelming dryness, resulting in Level 3's somewhat desert-like terrain. Bentham was kept here, despite his bounty being only 32,000,000.
In the middle of the level is a large hole going directly to Level 4 down below. This, combined with a gigantic fan directly above the hole, serves as the main ventilation system to redirect the smoke produced from below. Level 4 can be reached through this hole; however, to travel down it holds a risk of death or scalding by the fire and heat from the floor below.
Level 4: Blazing HellEdit
Blazing Hell (焦熱地獄 Shōnetsu Jigoku?, Inferno Hell in the Viz Manga) is the fourth level of Impel Down in which prisoners are kept. At this level, a pool lies filled with boiling blood heated by a raging fire making it extremely hot. The heat caused by this is so intense that it also heats up the level directly above it. If one tries to jump down to this level from Level 3 using the large hole used for ventilation above but do not land in a safe place, then they will die.
Prisoners from other levels are regularly tortured here. The most prevalent form of torture however is being thrown into the gigantic pot of boiling blood in the middle of the level. Other tortures involve prisoners being hung from ropes around their stomachs en masse and being dangled over the raging flames throughout the level, and being put to back-breaking hard labor by suppling giant logs of firewood to keep the flames going. Guards on this level must don protective gear to avoid being hurt by the intense heat, as it is strong enough to sear bared flesh. 
Daz Bonez was kept here, though he was shown to be unfazed by the heat of this level while being placed into hard labor. He also saw Luffy and Magellan's battle while in his cell.
Magellan, the warden of Impel Down, stays here. His office contains a lift, which can take several people to all the levels throughout the fortress, bypassing the stairs. This is also where the kitchen of the prison is located, right next to Magellan's office. Luffy's battle with Magellan was fought here prior to him being completely poisoned and captured.
Level 5: Freezing HellEdit
Freezing Hell (極寒地獄 Gokkan Jigoku?, Frozen Hell in the Viz Manga) is the fifth level of Impel Down in which prisoners are kept. This is the level where criminals with bounties of 100,000,000 and over are kept. In stark contrast to the level above it, the entire level here is a giant freezer. The level is so cold that not only do the prisoners kept here either freeze to death or lose pieces of their flesh from severe frostbite, but the food given to them is frozen to the level of being virtually inedible. Due to the extreme cold, Den Den Mushi do not function in this level, thus cutting off both contact and surveillance, except on the locations localized around the entrances that connects Level 5 to the previous and next levels. Along with the severe cold, the level is inhabited by wolves. These wolves roam around the level like the beasts of Level 2, where they were originally stationed at. However, they proved to be too brutal to be in Level 2 as they also hunted the other beasts as well, including the Basilisk and the Sphinx.
Along with the bitter cold of the level, there seems to be a occurrence of prisoners mysteriously disappearing as well. Prisoners who are incapable of moving by themselves have been disappearing without a trace. Because of this, the Impel Down staff and the prisoners call this phenomenon, the "demoning away." The superstition is that the missing prisoners have been actually pulled away by demons to the Gates of Hell itself. The belief of this superstition has been carefully kept within level 5 so that no inmates from the upper levels were aware about it prior to Bentham (disguised as Hannyabal), Buggy, and Galdino descending down to it where they were informed by the guards. Among these missing prisoners is Emporio Ivankov, the queen of the okama. He was imprisoned here until he mysteriously disappeared from his cell. Since then, he was rumored to be living in an abandoned guard's office deep within a forest situated in the level.
Luffy was transferred into the central tower of this floor after his loss against Magellan, with the effects of Magellan's poison whittling away his vitality, until released by Bentham, hoping to find a cure.
Level 5.5: Newkama LandEdit
Known as the The "Prisoners' Secret Flower Garden", Newkama Land (ニューカマーランド Nyūkamā Rando?) is a hidden sub level of Freezing Hell, and is where all the prisoners who have been supposedly "demoned away" have gone to. The secret area is located inside a rock between Levels 5 and 6. It was carved out long ago by a prisoner with a tunneling Devil Fruit power, and is a secret location unknown by the jailers. It is ruled by the "Queen" Emporio Ivankov, and it is called the Okama Paradise where all the okama and prisoners party and have fun all the time. It has been described by Ivankov as a "paradise within hell", and true enough, not one inmate from this hidden level is inclined at all to escape the jail as a result. However, since the level itself is hidden, the inhabitants seem to abide by very strict rules that prohibit them from actively interacting with the other levels, at least not without covert movement. Still, they do not seem to discriminate should new arrivals find their way here, as seen by the warm welcome they gave to Bon Kurei.
One of its main rooms is a combination of a sit-down cafe and a discotheque, with the main attraction being a cabaret stage where Emporio Ivankov and his followers perform. Apparently, there are also secret entrances existing from the other levels (save for Level 6) that leads directly into this hidden level which the inhabitants can use to their advantage in procuring any necessary supplies. The level also has a Surveillance Den Den Mushi that captures feeds from Impel Down's main surveillance system so the prisoners can see what is going on from all levels in the prison. They also steal newspapers from the prison's garbage cans to stay informed about current events.
Following the mass breakout of Impel Down, the residents of Newkama Land participated in the Whitebeard War and left for Kamabakka Kingdom, leaving Level 5.5 empty. However after two years, many prisoners are shown occupying it again, the only real difference being that it is now ruled by "Queen" Bentham.
Its name is a pun on "new comer" and okama, and refers to the okama who are completely able to change genders thanks to Ivankov's powers. In Japan, a "New Half" is a man who undergoes a "sex-change" operation.
Level 6: Eternal HellEdit
Eternal Hell (無限地獄 Mugen Jigoku?) is the lowest level of Impel Down. It is where prisoners who are insanely powerful, have caused crimes extremely atrocious, and/or whose mere existences have become a major threat to the World Government itself are kept. Sengoku said even a single Level Six prisoner lurking in a remote country could be an incredible danger to the public. The prisoners on this level have been given either the death penalty or a life sentence. They are basically "erased" from history.
Most high-ranking officers of Impel Down tend to avoid this level because of the danger these criminals pose, but will visit it if the need arises. The chief warden of Impel Down also has the authority to execute prisoners kept here on the spot if they begin acting up, and may do so at their own discretion. When he was chief warden, Magellan made no qualms about demonstrating this power by dousing prisoners with his deadly Hydra attack when they openly mocked his authority.
Ace was kept here on death row, awaiting his execution. Because most people dismiss Level 6 as just a rumor (until its actual discovery), Ace was believed to be on Level 5 by other prisoners. Jinbe was also placed on this floor, and was being kept in the same cell as Ace. Though the prisoners on this floor are either jailed for the rest of their lives or until their execution day arrives, Jinbe was only given a temporary sentence for refusing to fight against Whitebeard. Crocodile was also kept in a cell next to theirs. Near them are various other legendary pirates who hold deep grudges against Whitebeard, some of which are several imprisoned giants.
Kept alongside the prisoners was the former Head Jailer Shiryu. Because he constantly massacred prisoners, he was deemed to be a menace even within Impel Down, and became too dangerous to be kept anywhere else in the prison. For abusing his powers, he was sentenced to Level 6, until his death sentence. Interestingly enough, even though Level 6 is considered the worst hell, prisoners kept here are never actually tortured (though it was shown that Minotaurus occasionally showed up and tormented the prisoners with its club). It simply seems to be a holding cell for life or until an execution and prisoners do not have to endure terrible conditions (burning heat, freezing cold, etc.) unlike the higher floors. However, as seen with Jinbe and Crocodile as they moved through the other levels and are unaffected by those conditions, the inhabitants of this level may simply be too powerful to be affected by torture. On the other hand, Shiryu noted that the boredom of spending his time in this empty level made him wish for death.
Entering Impel DownEdit
Impel Down is located in the middle of the Calm Belt, where Sea Kings thrive, making entrance difficult. The only way to get there with the greatest of ease is to use the Tarai Current, 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 Shiki, almost no person wishes to ever go there. The only known exceptions are Monkey D. Luffy, Daz Bonez, and Crocodile. Jinbe believed that one or two lives should not be enough to make anyone want to venture into the prison, seeing Luffy's infiltration to rescue one person as incredible.
Usually, Impel Down is a hell-fortress with maximum defenses, making intrusion and breaking-out by criminals impossible. However, Luffy made the record of being the first to break-in, tarnishing that perfect record since Shiki's breakout twenty years ago. The Blackbeard Pirates are the second group of people to ever instigate a break-in, and they did so with less effort than Luffy, not having bothered to try to avoid detection.
Arrival and SterilizationEdit
When prisoners arrive in Impel Down, they are put in boiling water known as Hells Hot Tub to disinfect and sterilize them. This is ritualistically referred to as "baptizing" them. In the Viz Manga translation, it is instead said that only the prisoners' clothes are thrown into the boiling water.
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 Portgas D. Ace, Jinbe, and Crocodile.
Change of ClothingEdit
Most prisoners then have their clothes taken before they are given a striped black and white pair of shirt and trousers. However, they are permitted to keep certain articles of clothing and prosthetics, such as Galdino's glasses, and Crocodile's hook.
Exceptions to this rule are prisoners who were not meant to stay long before death. These include Portgas D. Ace, Monkey D. Luffy, and Shiryu. Jinbe was also allowed to keep his own clothing, as he was meant to be kept there until he was willing to cooperate with the World Government.
The residents of New Kama Land seem to have managed to retrieve their old clothes after escaping from their cells. Similarly, Crocodile seems to have somehow retrieved clothing similar to his old attire, including a long fur coat, almost immediately after escaping from his cell. However, it was revealed by Oda as well in the anime that Crocodile got his outfit back from New Kama Land.
Level Assignment and Life of TortureEdit
After sterilization and a change of clothing, the prisoners are then placed in one of the six 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. From then on, the prisoners are tortured in various ways, depending on their assigned levels, with most of them supposedly having no chance of ever leaving alive.
Whether outside people are permitted to visit the prisoners is unknown. Government agents and Marines have the authority to do so, but they would need permission from their superiors.
As Impel Down is a World Government facility, it is obvious pirates cannot enter without being branded as intruders and criminals. The Shichibukai are allowed, at the permission of the Government. Even so, they would be subjected to a full body search, then be forced to wear Seastone-cuffs, for safety measures. Without permission, such as Blackbeard and his crew, they would be considered as traitors. 
Leaving Impel DownEdit
Aside from visitors and Government officials, most people who enter Impel Down never leave there alive. The only prisoners ever allowed to leave are those who are held until their death penalty that takes place outside of the fortress (e.g. Portgas D. Ace), those who are meant to serve temporary sentence (e.g. Jinbe) and those who are released for special reasons (e.g. Arlong).
Breakout of Impel Down is virtually impossible, due to the defenses from the extremely powerful traps and guards of the place, with the Sea King-infested Calm Belt being its ultimate barricade. However, Shiki made the record of being the first person to break-out of the prison twenty years ago due to a mistake made by the Marines. Monkey D. Luffy became the second to do so.
Aside from his own escape, Luffy is also responsible for leading the very first mass-riot within the jail. Along with Emporio Ivankov, Inazuma, Buggy, Daz Bonez, Crocodile, Jinbe, Galdino, and 233 other prisoners, he is also responsible for the first-ever mass breakout in Impel Down's history. Bentham intentionally stayed behind, sacrificing himself to let the others complete their escape. It is unknown how many prisoners died during this riot, mostly from the Jailer Beasts and Magellan's poison.
Following this second breakout, the Blackbeard Pirates had freed several Level 6 prisoners for recruitment into their crew, leading to even more prisoners leaving.
A century before the start of the story, Morley was a wanted pirate who was imprisoned at Impel Down. Using his Devil Fruit abilities, he managed to escape the prison and construct a network of elaborate tunnels between Levels 5 and 6 of the prison, a fact that remained unknown for a long time allowing the prison to retain its status as being inescapable.
Twenty-two years before the start of the series, Shiki the Golden Lion became the first prisoner to escape Impel Down due to a mistake made by the Marines and by cutting off his own chained up legs. Ever since then, no prisoner had ever made a successful break-out or break-in until the eve of the Battle of Marineford.
Over the years, many prisoners of Level 5 would disappear for no apparent reason. The guards dubbed this phenomenon as "demoning" away, and thought such prisoners were gone forever. In truth, they were rescued from their cells by the Revolutionaries' commander Emporio Ivankov, who was also imprisoned in Level 5, and they all stayed at the secret Level 5.5, a space dug out by a past prisoner with a tunneling Devil Fruit power.
Head Jailer Shiryu of the Rain killed many prisoners within the walls of the prison for his sheer pleasure, and was deemed a menace. He was put on death row, and was held in Level 6 until his sentence would be carried out.
Water 7 SagaEdit
Enies Lobby ArcEdit
Impel Down was briefly mentioned by Nami as a place that once a person goes in will never come out. She thought Robin was going there but it turned out to be wrong. Later in Enies Lobby, Spandam ordered Franky to be sent to Impel Down while Robin was to be sent to the Marine Headquarters.
Miss Goldenweek's "Operation: Meet Baroque Works"Edit
Thriller Bark SagaEdit
Thriller Bark ArcEdit
Summit War SagaEdit
Impel Down ArcEdit
Sometime around Ace's imprisonment, Buggy the Clown was captured by the Marines and sentenced to Level 1. His crew was thinking of saving him, but due to Impel Down's reputation of impregnability, they gave up and left him.
During the preparations for Ace's impending execution, Jinbe of the Shichibukai was sent to Level 6, as he refused to fight on behalf of the World Government, and even broke out in rage at Marineford. He was placed in the same cell as Ace, whom he was friends with for a long time.
After the consecutive mass break-outs (the first led by Luffy and Buggy, the second by Blackbeard), Impel Down was left completely defeated.
After the war with the Whitebeard Pirates, several Level 6 inmates would escape due to Blackbeard's death match and the warden, Magellan, would be beaten to an inch of his life. Among the escapees was Shiryu, who Magellan temporarily released out of desperation for assistance in quelling the riots. However, Shiryu quickly betrayed Magellan and teamed up with Blackbeard, as well as many more Level 6 inmates, who would all ultimately go on to inflict the final killing blows upon Whitebeard.
Fish-Man Island SagaEdit
From the Decks of the WorldEdit
After the time skip, Impel Down has been repaired from Luffy's and Blackbeard's mass escapes. Hannyabal has been promoted to chief warden and Domino has been promoted to head jailer. Another Jailer Beast, Minochihuahua, has been added. Saldeath has grown taller and Sadi has fallen in love with the newly appointed vice warden, Magellan who has been demoted (or has stepped down) to vice warden.
Jean Ango, a bounty hunter, became very active in hunting down many of the escaped prisoners and sending them back for the bounties, including many Level 6 prisoners, and desired to capture the main perpetrators of the breakouts two years ago.
After Donquixote Doflamingo's defeat at the hands of Monkey D. Luffy and Trafalgar D. Water Law, he was sent to Impel Down. Though nearby, a pirate ship flying Kaido's jolly roger commanded by Captain Jack pursued Doflamingo's escort of four Marine warships, as Jack planned to take him back by force. However, the rescue attempt failed, and Jack was presumed dead for some time. Doflamingo was put in Level 6 and he started looking for the latest news from the outside world since Tsuru rejected his request to have newspapers delivered to him.
As the royal parties arrived at Mary Geoise for the Levely, Doflamingo was shown in a solitary cell. He asked Magellan if he was guarding him and wondered if an assassin would be coming to kill him before he could reveal the truth about the Mary Geoise's national treasure.
Translation and Dub IssuesEdit
Impel Down's title is often translated as "the Great Gaol", "gaol" is an old English word for "jail" or "prison".
Anime and Manga DifferencesEdit
In the anime, there are two additional animal guards placed in Level 2: a giant praying mantis who slices with its sickle-like appendages and a small hippo who can extend its jaws widely to swallow prisoners whole.
Galdino stated in the anime that the sand in Level 3 is actually the remnants of prisoners who had dried up and died.
When Level 5 was introduced in the manga, it showed a prisoner whose finger froze, cracked and fell off, causing another prisoner to laugh at him for having a frostbite, in the anime the prisoner simply could not feel or move his finger anymore.
In an anime-only flashback of 20 years ago, when Hannyabal first joined the prison, the first prisoner he was assigned to deal with was Olive. She seduced him to lower his guard, and then tied him up and stole his clothes in an attempt for freedom (a reminiscence of what Bentham would do in disguise as Nami 20 years later), but was foiled when Magellan caught her, and she was locked up.
- The symbol of Impel Down is an overlap of the prison name's initials, "I" and "D".
- Impel Down prisoners are assigned a 4-digit number preceded by a single letter that appears to denote what floor the prisoner is to be held at, starting with E for level 1 and presumably ending with A for Level 5. It is unknown what letter would be given to Level 6 inmates, or if they are even assigned numbers.
- Various influences of "Hell" are present within its walls:
- 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.
- The description of Mount Purgatory from Purgatorio, the second part of the poem, highly resembles Impel Down's design.
- Level 3: Starvation Hell is ironically the third floor, while in Dante Alighieri's hell, its the place where who was damned by the sin of gluttony are punished by "starving to death" inside Cerberus's gullets.
- Level 4: Blazing Hell is a typical representation of Hell in cultural and fictional references, with intense flames and heat burning the "sinners" (or in this case, prisoners), while a demonic figure (in this case, the Jailer Beast Minozebra) pushing sinners into the flames. Magellan's residence on this level could refer to this depiction of hell being where the devil resides. This resembles, in Dante's tale, the level Violence where violent people are punished: a lake of boiling blood, where the damned are drowning.
- Level 5: Freezing Hell is another thing that is based on Divine Comedy known as Treachery where the most evil figures are punished. In fact, this level is the one where the damned are fraudulent. With the only difference that the Dante's damned are totally frozen into a lake of ice and in the Divine Comedy it is known to be the lowest level of Hell.
- A few of the levels of Impel Down also seem to resemble Buddhist concepts of hell such as the Crimson Hell which seems based on the "Hell of the Sword Tree and Knife Hill" which similarly tortures its victims by forcing them to run upon or impaling them upon trees and hills covered with knives and swords. Also the Four Jailer Beasts seem to resemble the Jailer Beasts Horse Face and Ox Head.
- 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.
- Newkama Land is a reference to the movie The Rocky Horror Picture Show, in which main character Frank N. Furter is a transvestite similar to Newkama inhabitants. In the final scene of the movie, the heroes Brad and Janett surrender to their transsexual feelings in a similar way as Ivankov's candyboys accept their true inner selves.
- Level 5.5 is a pun, as it is pronounced Go Ten Go. "Goten" means "Roaring Heaven", and Level 5.5 was portrayed as heavenly.
- Two names, Roche Tomson and George Black were shown on a list of prisoners on Level 5. These prisoners were never seen, and their fates are unknown.
- Roche Tomson's name is similar to that of real-life pirate Roche Braziliano, a Dutchman who sailed in Brazil and was noted for his extreme sadism, even amongst other pirates. Also, Braziliano was at one point caught by Spanish forces, as was Tomson by the World Government, only he escaped and eventually disappeared.
- Roche Tomson's number on the list of prisoners in Impel Down is 6581.
- The level 6 purpose of erasing a person from history is similar to the damnatio memoriae, a form of punishment in the ancient Rome which had the intent of erasing the memories a person and everything that could carry it to the future generation, effectively erasing the existence of a person from history.