The infernal regions, described in the Iliad as situated as far below Hades as heaven is above the earth, and by later writers as the place of punishment for the spirits of the wicked. By the later poets, also, the name is often used synonymously with Hades, or the Lower World in general.

In mythology it is the infernal region further down than Hades where Zeus supposedly confined the Titans.

The deepest abyss in Hades. Where Kronos was imprisoned.

a place where the wicked are punished after death

Greek for the place of eternal punishment but in 2Pe 2:4 applied to the intermediate sphere of punishment for fallen angels (Latin Tartarum).

Tartarus is the Greek name for an underworld for the wicked dead; another name for Gehenna or Hell.

In classic Greek mythology, below heaven, earth, and hades is Tartarus, or Tartaros (Greek Τάρταρος, deep place). It is a deep, gloomy place, a pit or abyss used as a dungeon of torment and suffering. While almost all the dead were said to go to hades, the gods cast the very worst mortal sinners and immortal enemies into tartarus for endless punishment.