Avici

In Buddhism, Avīci (Sanskrit and Pali for "without waves" – Japanese and Chinese: 無間地獄, Wújiàn dìyù and 阿鼻地獄, Ābí dìyù) or Avichi, is the lowest Level of the Naraka or "hell" realm, into which the dead who have committed grave misdeeds may be reborn. It is said to be a cube 20,000 yojanas (120,000 to 300,000 kilometres) to a side, buried deep underneath the divine (nonvisible) earth.Avīci is often translated into English as "interminable" or "incessant", due to the idea that those beings which have been sent there languish there eternally. The other hells function more like Purgatory, where after perhaps a few aeons of suffering, one might be reborn as some sort of lowly life-form in a somewhat less horrible place; but, those sent to Avīci Hell are thought to be hopeless of any respite.

There are various evil acts which can lead one to be committed to the eternal torments of the Avīci Hell. People reborn in Avīci generally have committed one or more of the Five Grave Offenses:

Buddhism teaches that rebirth into Naraka is temporary, while the offenders works off the karma they garnered in life. Rebirth into Avīci hell is not eternal. However, the Lotus Sutra provides an example of humans who have to endure long-term suffering in Avīci. Some sutras state that rebirth in Avīci will be for innumerable kalpas (aeons). When the offender passes away after one kalpa, it is reborn in the same place, suffering for another kalpa, and on and on until it has exhausted its bad karma. For this reason, Avīci hell is also known as the "non-stop way" (無間道).

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Wikipedia