Tartarus was the lowest level of the Ancient Greek Underworld, where Hades is the ruler of. It is the final destination for lost souls and a prison for those damned by Zeus. The Gates of Tartarus were located beneath Themyscira and were guarded by Queen Hippolyta and her immortal Amazons.
When the Olympian Gods started the war with the Titans, the god Hades made a bargain with the enemy to gain control over humanity. He tricked Hippolyta, whom he loved, to open the gate to Olympus. However, the Titans were eventually defeated and he was hrown along with them into Tartarus to rule over the dead and never escape.
To remind her of her lover's treachery, Hippolyta was ordered to guard the entrance to Tartarus and its key. To make sure Hades stayed in Tartarus, she split up the key and hid it across the world. Although most have to enter Tartarus just to talk to those inside, powerful beings like Felix Faust or Hades could create a portal with which they could communicate through.
- "Fire From Olympus" (Mentioned Only)