Tartarus

Tartarus was born together with Nyx, Erebus, Gaea, and Eros ("Love"), out of Chaos.

Tartarus was the personification of the darkest and deepest region of the Underworld. This was the region where Uranus had thrown the Hundred-Handed giant and the Cyclopes. Later, this was where Cronus and the other Titans who had opposed Zeus were imprisoned and guarded by the Hundred-Handed giant.

See Creation, Theogony of Hesiod.

By his sister Gaea ("Earth"), they were parents of the monsters – Typhon and possibly Echidna.