The Ring of Namira is a Daedric artifact bestowed by Namira upon those who do her bidding. The ring has been known to, at times, reflect damage back onto an attacker, while at other times being able to increase a person's stamina and restore their health if the wearer cannibalizes a corpse.
In 3E 405, an agent of the Blades was awarded the ring by Namira in return for killing a vampire ancient that had fallen out of favor with the Prince. In 3E 433, the Champion of Cyrodiil was tasked by Namira to kill a group of priests of Arkay who were attempting to convert her followers in the ancient Ayleid ruin of Anga; once the task was complete, Namira awarded the champion her ring. In 4E 201, the Last Dragonborn was awarded the ring for bringing a priest of Arkay to Namira's shrine in Reachcliff Cave, and then killing and eating him.