Garnag was an Orsimer assassin for the Dark Brotherhood, residing in the Cheydinhal Sanctuary at the time of the Great War. He brought the Night Mother's crypt from Bravil after it was raided, and was one of the last surviving members of the Brotherhood in Cyrodiil.
Garnag was sent to aid Listener Alisanne Dupre and others in the defense of the Night Mother's Crypt in Bravil in Sun's Dusk of 4E 188. It was overrun later that month, with Dupre and Andronica perishing while defending it, and Garnag alone surviving. He was gravely injured and lost his right eye, but managed to transport the Night Mother back to Cheydinhal.
In the aftermath of Alisanne's death, Garnag murdered Sanctuary leader Rasha at the request of Cicero, when Rasha falsely claimed to be the new Listener in 4E 189. Garnag, Cicero, and Pontius were the only members remaining in the sanctuary, and Cicero went mad shortly after. Garnag later left the sanctuary in 4E 191 to look for food, but failed to return after three months. His fate is unknown, with Cicero still receiving no contact of him by 4E 192. but if he still lives, he is likely the only surviving member of the Dark Brotherhood outside Skyrim.