A piece of unearthed regalia, Duul Do Nahlot was carried by Dragonborn from long ago. The dragon Nahlot ravaged the Northern coast of Skyrim. Dawnstar sent ships out to fight him but all fell before Nahlot.
Mages lured Nahlot into a trap where the Thane of Winterhold defeated him. He kept the severed horn (or "crown") of Nahlot as a badge of office, using it to punish guards for impudence. Years later he was eaten by a giant mudcrab in Morthal.
Thereafter, Duul Do Nahlot passed from one warrior to the next, each one engraving it with the sigils of their allegiances.
Replacing the ShutUpper, this weapon will incur no bounty when used, nor is it hostile. It silences any NPC and sends them flying away from you -- unharmed, but humbled.