The Crown of Horns is an evil, intelligent artifact of great power from the Forgotten Realms Dungeons & Dragons campaign setting. Forged by a Netherese arcanist and enchanted by Myrkul, the former god of the dead, it carries with it a long history of corruption and tragedy.
At one point, the Crown possessed Laeral Silverhand, one of the Seven Sisters, and was sundered by her husband, the archmage Khelben "Blackstaff" Arunsun, who locked its pieces away within the heavily-protected walls of his tower. However, when Myrkul died at Midnight's hand during the Time of Troubles, the god tore the broken shards of the 'Crown' from Blackstaff Tower, reforged it in a new shape, and infused it with the remains of his sentience before teleporting away. To this day, Myrkul, through the Crown, has been spreading evil through the Realms, tormenting members of the Church of Cyric as well as hapless innocents.
The Crown of Horns appears as a silver circlet with a black diamond set on the brow and four bone horns mounted around its edge. It imbues the wearer with several considerable necromantic powers - including the unique "Myrkul's Hand" property - but has a tendency to strongly influence that action of the wearer, changing his alignment to neutral evil and gradually making him into an undead creature, among other things.
The Crown of Horns was last seen in the possession of a yuan-ti pureblood named Nhyris D'Hothek, who disappeared from his haunts in Skullport in 1370 DR, after the Crown transformed him into a lich. People and creatures who have remained dedicated to Myrkul after, or have become dedicated to him since his demise, devote themselves to him through the Crown of Horns and are known as 'Horned Harbingers' - Nhyris included. The statistics for the Crown can be found in the Forgotten Realms 3rd edition book 'Magic of Faerun'.