The Keys of Hades are magic "keys" owned by the god Hades. They have the power to "seal" or "free" people in the Underworld, which means someone can bring someone from or send someone to the Underworld or Tartarus using the keys.
One of the keys was placed inside the Sword of Hades. It is said that one touch of the sword can send or release a soul to and from the Underworld. The sword was stolen and Persephone feared that anyone who possessed it could release anyone from the Underworld, as the sword possessed a key of Hades which had such power. After Percy Jackson retrieved it through the events of Percy Jackson and the Sword of Hades, it is revealed that Hades had no part or knowledge in its creation. Knowing it would upset the balance of power between the Big Three, he was angry with Persephone for having it forged. Despite this, it is assumed that he had used this same sword, the key included, in the Battle of Manhattan.
|Personal Weapons:||Riptide | Annabeth's Knife | Backbiter | Frank's Spear | Hazel's Spatha | Katoptris | Nico's Sword | Thalia's Spear | Aegis | Maimer | Kronos' Scythe | Ivlivs | Master Bolt | Poseidon's Trident | Sword of Hades | Reyna's Spear | Hades' Staff | Juno's Gladius | Drakon Bone Sword|
|Magical Items:||Annabeth's Yankees Cap | Helm of Darkness | Keys of Hades | Flying Chariot | Golden Apple | Greek Fire | Hermes' Multivitamins | Leo's Magical Toolbelt | Nectar and Ambrosia | Pandora's Pithos | Winged Shoes | The Golden Fleece | Stygian Ice Whistle | Serapis' Staff|
|Spoils of War:||The Minotaur's Horn | Medusa's Head | Kampê's Scimitars | Nemean Lion's Pelt | Gorgon Blood | Cornucopia|
|Items:||Camp Necklace | Chameleon Armor | Daedalus' Laptop | Golden drachma | Mark of Athena | The Pax | Video Shield | Wristwatch Shield | Golden Mango | Sibylline Books|
|Blessed Metals:||Celestial Bronze | Imperial Gold | Stygian Iron|