|Guild Master Mercer Frey|
|Previous Ruler||Gallus Desidenius|
Mercer Frey was a Breton thief and skilled swordsman who lived during the second and early third centuries of the Fourth Era. He began his career of thievery as a member of the Thieves Guild in Skyrim, where he learned from Guild Master Gallus Desidenius. His mentor was also secretly a member of the Nightingale Trinity, a group which Mercer was eventually inducted into. Mercer would go on to betray the Nightingales and Nocturnal by desecrating the Twilight Sepulcher and taking the Skeleton Key for himself. He then used the key to commit crimes against the guild until his activities were discovered by Gallus around 4E 176. In retaliation, Mercer murdered Gallus, framed another Nightingale, Karliah, and took his late mentor's place as Guild Master. He hunted Karliah for over two decades; she, in turn, did her best to undermine him and his allies. In 4E 201, with the help of a new guild member, Karliah exposed Mercer, reformed the Nightingale Trinity, and finally killed him.
- For game-specific information, see the Skyrim article.