In appearance, the Skeleton Key doesn't always take the form of a key, and sometimes manifests as a lockpick instead. In its key form, it can be used to unlock any lock. As a lockpick, it is nigh unbreakable and can get past even the toughest locks. The two limitations placed on the Key by wizards who sought to protect their storehouses were that the Key could only be used once a day and it would never be the property of one thief for too long, eventually disappearing.
The artifact functions as a tool for "unlocking" all things, including portals, hidden potential, and other unknown possibilities. Its ultimate function, however, is to unlock and hold open the Ebonmere, a portal to Nocturnal's realm, Evergloam, located in the Twilight Sepulcher of Skyrim. The Nightingales are tasked with guarding the Sepulcher and retrieving the Key should it be stolen. Unfortunately, the Prince is said to allow the Skeleton Key to be stolen or lost periodically, whether by purpose or apathy.
According to pre-ri'Datta Khajiiti myth, sometime after the death of Lorkhaj, Noctra (Nocturnal) was born of his black blood at the steps of the Void Gate. Boethra battled her "until she knew she was not Namiira", and when the fighting subsided, Noctra was brought before Azurah to be judged. Azurah allowed Noctra to live so long as she served Azurah and the ja-Kha'jay. Instead, when the opportunity was right, Noctra stole the Skeleton Key from Azurah and fled into the void.
The first supposed wielder of the Key was the thief Arrovan. After disappearing, the Key always chose inaccessible places to hide, and for the benefit of historians Arrovan made a list of the various resting places.
In the mid-Second Era, the key was in the possession of Sotha Sil, who kept it in his Clockwork City. Nocturnal tried to take control of the Clockwork City in 2E 582. She summoned Sotha Sil's Shadow, who replaced him as ruler of the Clockwork City. Meanwhile, a Clockwork Apostle, Chancellor Gascone Dusant, sought to deliver the Skeleton Key, which had been accidentally found by a Factotum beneath the Brass Fortress, to Clavicus Vile, only for the Key to be stolen by the Blackfeather Court. The Vestige, assisted by Divayth Fyr and the Clockwork Apostles, unveiled the plot, but were unable to reclaim the Skeleton Key before it was taken by Sotha Sil's Shadow.
Nocturnal and the Shadow then attempted to seize control of the Clockwork City by using the key to try unseat the real Sotha Sil from his control center, the Throne Aligned, and have the shadow take over it. The Vestige and Proctor Luciana Pullo intervened and defeated the shadow in combat, but Nocturnal had her shadows envelop the area as a countermeasure, in an attempt to consume the heroes. Luciana refused to yield, and used her shadow-banishing light to keep Nocturnal's shadows at bay. Divayth Fyr arrived at the last second and kept Sotha Sil alive and constrained the shadow. They bought the Vestige enough time to remove the Skeleton Key from the Throne Aligned and awaken Sotha Sil, who then reunited with his shadow and banished Nocturnal from his realm. After thwarting Nocturnal's plot, Sotha Sil declined the Vestige's request to have the Key as a reward, and instead entrusted it to Divayth Fyr to keep it away from Nocturnal's clutches for as long as possible. A replica of the Skeleton Key was created for the Vestige, however, as thanks for their aid.
During the Imperial Simulacrum, the Skeleton Key was uncovered a number of times. The Eternal Champion discovered the artifact in either Valenwood or the Summerset Isles while following rumors of the Key having appeared in one of the known dungeons. The key was then recovered in Hammerfell by the Spire Thieves of Broken Wing sometime during The War of Bend'r-mahk. In 3E 397, the Soul of Conflict invaded Broken Wing and exterminated the Spire Thieves. Within the dungeon, they located the Key within their treasure troves.
In the events leading up to the Warp in the West, an unknown agent of the Blades was tasked by Nocturnal to kill a mage in their stronghold in return for the Skeleton Key. However, the mage had already had a contingency plan in case the Daedric Prince had sent someone to slay them. They created a fake artifact (Auriel's Bow, Staff of Magnus, or the Warlock's Ring) that functioned identically to the true artifact to tempt the agent with, though it would degrade after several days; enough time to flee when the illusion was broken. Accounts conflict if the agent took the mage up on the offer and was bamboozled, or if they slayed the mage and received the Key in return.
The Key later came into the possession of Gentleman Jim Stacey while he lived in Hammerfell. He later became the leader of the Thieves Guild in Vvardenfell. By 3E 427, the Camonna Tong allied themselves with the Fighters Guild Master in Vvardenfell, Sjoring Hard-Hart. The alliance used the Fighters Guild as an extension of the Camonna Tong's influence, hunting down and eliminating the struggling Thieves Guild to prevent them gaining a foothold in Vvardenfell. It is rumored that after Hard-Heart and his lieutenant's corruption was discovered, they were brought to justice - though it is unknown if this was the work of the Thieves Guild or an internal cleansing by the Fighters Guild. Scholarly documents contradict the victory against the Camonna Tong, instead stating that the corrupt Fighter's Guild and the Tong wiped their opposition out. Regardless, the Skeleton Key was either taken from Gentleman Jim Stacey's corpse after his loss, or he passed on the Key to the next Thieves Guild Master after their victory.
Circa 3E 433, an artifact known as the Eye of Nocturnal was stolen from Nocturnal's shrine in Cyrodiil's Blackwood region. Nocturnal tasked the Champion of Cyrodiil with recovering it. The thieves, an Argonian couple in Leyawiin, hid it in a flooded cave in Topal Bay. The Champion returned it to Nocturnal and was rewarded with the Skeleton Key.
Some time before 4E 201, the Key was stolen from the Twilight Sepulcher by Mercer Frey, a corrupt Nightingale. Its long-term loss resulted in a decline of the Skyrim branch of the Thieves Guild due to bad luck without Nocturnal's influence. The guild's influence declined until their only presence was in the Ratways beneath Riften. Mercer used the Key to bring himself luck, but he was eventually confronted by the Nightingales beneath the Great Statue of Irkngthand. Mercer was killed, and the Last Dragonborn brought the Key back to the Sepulcher, reopening the Ebonmere.
- Martin's dialogue during Blood of the Daedra in Oblivion
- The Dark Spirits — Amun-dro, the Silent Priest
- Arena/Daggerfall in-game description
- Karliah's dialogue in Skyrim
- The Nightingales Vol. 1 — Gallus Desidenius
- Artifact Dialog — The Imperial Library
- Events of ESO: Clockwork City
- Skeleton Key Replica, obtainable from Razoufa after completing the Clockwork City Story Quests in ESO
- Events of Broken Wing in Shadowkey
- Nocturnal's quest in Daggerfall
- Events of the Fighters Guild questline in Morrowind
- Fighters Guild and Thieves Guild quests both having the same objective in Morrowind
- Myth or Menace?
- Kill the Master Thief quest in Morrowind
- Nocturnal quest in Oblivion
- Thieves Guild questline in Skyrim