To find the Daedric Crescent Blade (a legendary item) go to Tel Fyr. On a table beside Devithe Fyr there is a key to plunder the dungeon, take the key he wont mind. Plunder the dungeon until you find the Daedric sanctuary amulet. Put the amulet on and it will teleport you to a daedric shrine. Once there beat the dremora and it will appear in your inventory.