Tartarus

Special Prison For Villain Criminals - Tartarus (犯罪者持殊収監施設タルタロス) is a prison located far away from civilization, where extremely dangerous Villains are imprisoned and interrogated under the highest security standards possible.

Description
The high-security prison appears to be located on an island, surrounded by giant walls. The only access to the prison is a bridge with the entrance guarded by two or more guards that check every vehicle going in.

Sensors are continuously monitoring the vital functions of prisoners, reacting to even the slightest sign of unusual behavior or attempt to activate a Quirk.As seen in Episode 50, guards will also monitor prisoners as a failsafe, and judging by the weapons they carry, are authorized to use lethal force.

Tartarus's interior is heavily armored with blast doors lining narrow, steel-plated hallways. Prisoners incarcerated inside Tartarus are heavily restrained, sitting down on a large, high-tech chair with a full-body strait jacket. Prisoners may be manually kept alive through oxygen masks, IV fluids, and feeding tubes, such as All For One. The aforementioned sensors are also connected to four ceiling-mounted, automated machineguns that will fire on the prisoner if they suddenly move or have thoughts of activating their Quirk.

History
Not much is known about the history of the prison yet.

After the Hosu Incident, the villain Stain was sent to Tartarus.

After the Vanguard Action Squad Invasion, the villains Muscular and Moonfish were sent to the prison. Moonfish is awaiting the death penalty.

After the Kamino Incident, the villain All For One was sent to Tartarus. All Might later went to meet him within the prison to discuss unresolved matters between the two.

After the Shie Hassaikai Raid, the villain Overhaul was sent to Tartarus.

After being captured by Gran Torino and the detective Naomasa, Kurogiri was sent to Tartarus. Once there he show no sign of confessing or disclosing anything about the League of Villains.

Prisoners
The prisoners are criminals for whom the death penalty is not enough. They are kept underground, watched by a multitude of sensors and guards in a big, clean white room. For a certain time limit, the villains may receive visitors. There have been at least 1,541 prisoners in Tartarus. Known prisoners include:

Trivia

 * Seiji Shishikura's father is employed at Tartarus. Futhermore the main reason Seiji ended up attending Shiketsu High School is because the school provides the students with hats which are very similar to those Tartarus employees like his father wear.
 * In Greek Mythology, is a dungeon in the underworld where the worst sinners (including the Titans) are forever kept to be tortured for their evil deeds.
 * The manga and anime say that this was the name of the god who ruled it, however this is mistaken, as his name was Hades. This mistake was corrected in the dub.
 * It should be noted that while Hades ruled over Tartarus, the original master (and namesake) of the realm was a primordial Deity who predated both the titans and the Olympians (Greek gods; including Hades); with Hades taking control of it later on, along with the other sections of the Greek underworld. These areas became collectively known as Hades (which in later translations into Latin and English, likewise became Hell).