A ring of Myrkul was a relatively thick gold band painted black adorned with an image of a white flaming skull.
These rings were popular centuries ago in the Savage North when individual cells of the Faithful of Skulls desired secrecy to protect themselves. The rings were used to identify fellow Myrkulites and augment their powers while they were on missions. With the destruction of the Faithful of Skulls in 1020 DR this magic item ceased to be used as the new Church of the Bone Lord preferred to operate openly, but many of these items continue to be found throughout the Savage North, but in particular within the Sword Coast North around Waterdeep and Neverwinter (among the Bone Wing Heresy).
Rings of Myrkul served as keys for priests of Myrkul to enter a temple of Myrkul safely. They also allowed the wearer the ability to walk among the undead without being attacked (unless the wearer attacked the undead). Additionally, the rings had a few offensive abilities, including casting the spells chill touch and ghoul touch. Before the Time of Troubles (1358 DR), the rings had greater necromantic powers that could be invoked by Myrkulites, but after the Time of Troubles those powers disappeared.
The Rings of Myrkul around the Mere of Dead Men have been tied to the ruins of Uthtower by some ritual devised by Chardansearavitriol, (The Dracolich Ebondeath) and gain additional powers when within the Mere. When Myrkul was killed in 1358 DR, our secret temple in the Mere of Dead Men in the Sword Coast North sank into the swamp. The priests escaped into the Mere but were killed, their rings falling into the possession of the beasts of the Mere. Around 1370 DR, the cleric Varak Redshield found a ring of Myrkul in the Holk House in the Mere of Dead Men. Several other rings have also been found in the Mere.