The Gray Cowl of Nocturnal is a daedric artifact that once belonged to Nocturnal. It takes the form of a dark leather cowl, which obscures the face of the wearer. Nocturnal is revered as a god by thieves across Tamriel. Her reputation as the Mistress of Shadows has sometimes led thieves to attempt to steal an item from her to prove their greatness. As Nocturnal is usually depicted wearing a cloak and a cowl, it is around these two items that legends have arisen. The story of the theft of Nocturnal's cloak is probably fiction, as is at least one story of the theft of the cowl, but the cowl is known to have left her possession. It appears to have been stolen by a thief named Emer Dareloth, the first guildmaster of the Thieves Guild, although a curse bestowed upon the cowl by Nocturnal meant that the name of cowl's owner is lost to mortal memory. "Whosoever wears it shall be lost in the shadows. His true nature shall be unknown to all who meet him. His identity shall be struck from all records and histories. Memory will hide in the shadows, refusing to record the name of the owner to any who meet him. He shall be known by the cowl and only by the cowl." This curse was broken when history was rewritten through the use of an Elder Scroll.
The cowl is inscribed with the phrase "Shadow hide [y]ou" written in the Daedric Alphabet, though as is common in the Daedric alphabet, the letter Yahkem (Y) is omitted from the inscription. The phrase is also used as a code between thieves, either as a form of praise to Nocturnal or a literal expression of hope. The Nightingales of Nocturnal believe the true meaning of the phrase is a reference to their fate after death, when their souls journey to the Evergloam and become one with the shadow, the cloak that covers their fellow thieves. The Office of the Unseeing Eye, a section of the Cult of the Ancestor Moth, expressed a desire to find the cowl in order to see if the curse does exist, and research further on how to remove it.
After having been stolen by Emer Dareloth, the cursed cowl was handed down from one guildmaster to the next in the Cyrodiil branch of the Thieves Guild. This forced the guildmasters to work under the persona of the Gray Fox. Thought to be a myth by most members of the public, the identity of the Gray Fox came about over the course of three hundred years, as the guildmasters lost their individual identities and became known only as the bearer of the Cowl. Legends propagated around the mysterious master thief, who was thought to possess immortality and supernatural thieving abilities. He was viewed as a hero by the beggars and the lower classes of Cyrodiil, but he was hated by the nobility and the Imperial Watch. The curse was broken in 3E 433, when Count Corvus Umbranox, the contemporary Gray Fox, organised the theft of an Elder Scroll from the Imperial Library in the Imperial Palace. Umbranox used the Scroll to rewrite history and remove Nocturnal's curse. Without the curse, the past guildmasters were able to work openly, and the Thieves Guild became more prosperous. Umbranox regained his identity and his title as Count of Anvil, and the Cowl was passed on to a new guildmaster. Even without the curse, the Cowl still had the ability to cloak the true identity of the wearer, and it was still identified with the infamous Gray Fox. By 4E 201, the Gray Fox remains a revered character among thieves.
At an unknown time, the Gray Cowl made its way into Skyrim, and so did the mantle of the Gray Fox to a Nord by the name of Pjofr Ice-Blade. Instead of becoming the head of the Ice-Blade clan, he left it, pursuing his own interests out of greed, and as a result the clan declined.  Scoundrels then targeted the Ice-Blade clan, attempting to steal their wealth. Erikur, the Thane of Solitude along with other conspirators plotted to kill Pjofr’s sister, leaving her son, Smaref, as easy pickings. By 4E 201, They succeeded in making her cause of death look like it was due to an illness. Smaref was left an orphan and last of the Ice-Blades, and the scoundrels began manipulating him. They obtained the boy’s consent to transfer his family’s lands over to them, and sent him to Riften.  After hearing of the passing of his sister, Pjofr wanted to step into Smaref’s life and take the role of his guardian. He investigated from the sidelines, he heard of Smaref’s adoption by one of Riften’s wealthy. He saw that while his new father figure was caring, his wife considered the child nothing but a street urchin. He was let into their household for dinner one day, and saw that the wife wasn’t good for Smaref. She revealed that Bolli was asked to take in the child for adoption by Solitude’s Jarl. Pjofr investigated further into this and discovered the plot to strip the Ice-Blades of their wealth.
Pjofr decided that the person that deserved to inherit the Gray Cowl of Nocturnal was the person who was willing to help him get back at Erikur, and faked the death of the Gray Fox. A stranger investigated the grave of the Gray Fox, and discovered a note that it was a fabrication, and took up the task to gain the Cowl. Following Pjofr’s instructions, the adventurer swiped various important documents with fabrications, ruining the scoundrel’s claims to the Ice-Blade clan’s lands. Finally, the adventurer delved into the Nordic ruin of Silverdrift Lair, and took The ancestral Sword of Clan Ice–Blade, so that Pjofr could prove his ancestry. With the tasks done, the adventurer returned to the Gray Fox’s grave, and Pjofr came in-person to grant the Cowl to them, passing on the Gray Fox’s mantle.
- The Gray Cowl of Nocturnal's identity-concealing properties are referenced in The Gray Fox card, which lacks a known creature subtype.
As seen in Oblivion
- Hiding with the Shadow
- Purloined Shadows — Waughin Jarth
- Song of Hrormir
- Instructions: the Gray Cowl — Office of the Unseeing Eye
- The Gray Fox's dialogue during the Oblivion Crisis
- The Nightingales Vol. 1 — Gallus Desidenius
- Events of Oblivion
- Appearance of a bust of the Gray Fox in Skyrim
- Stranger's Journal — Pjofr Ice-Blade
- Letter to Gisli — M
- Nivenor's Journal — Nivenor
- The Gray Cowl Returns! Creation for Skyrim Special Edition