Impel Down, also known as the Underwater Prison and the Great Prison, 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 and part of the Tarai Current.

As a matter of fact, the structure of Impel Down prison actually extends all the way to the ocean floor. What we’ve seen on the surface is actually just the entrance of the building. There are six more levels below the water, each act as prison for some of the most dangerous criminals in the world. Level 1 is closer to the surface, while level 6 lies at the bottom of the ocean.

A prisoner’s assigned level is usually determined by the bounty value on his or her head. Along with various group and solitary 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.

These 6 levels of Impel Down remind me of the 5 elders and Imu. The 5 elders and the first 5 levels of Impel Down line up too well.

Level 1: Crimson Hell – Spiders chase you while you are cut by razor sharp trees.

– Saturn is a spider and his attack seems to be some kind of super sharp stab or poke.

Level 2: Wild Beast Hell – Wild beasts go around beating the shit out of you.

– Mars turns into a bird like the basilisk and is in charge of nature and what’s more natural than wild beasts (Possibly Warcury cuz he’s kind of a wild beast and we had the Minotaur)

Level 3: Starvation Hell – A barren wasteland with no food or water.

– Ju Peter is in charge of agriculture and is literally a sand worm.

Level 4: Blazing Hell – A place that is on fire that has a pot of boiling blood.

– Warcury is a giant pig and they get roasted. I don’t think we have seen Warcury’s powers yet, and think he has some kind of fire ability or heat ability which could also be why Red Roc didn’t do much damage too. (Possibly Mars cuz he’s got some fire power).

Level 5: Freezing Hell – Frozen wasteland.

– Nusjuro uses the same ice cold powers that Brook does or just that ice cold appearance too.

Where I am going with this is I believe the sacrifices and/or blood spilled in the individual respective hells is the source of power for the elders. Those magic circles looked real blood magic esque and I think there is a direct link.

Imu could be a representation of level 6 because prisoners there are essentially erased from history as Imu erases islands.