Otar the Mad is a Dragon Priest that appears in The Elder Scrolls V: Skyrim. He appears in Ragnvald.
Otar was an ancient Nordic chieftain who ruled over the city of Ragnvald in the Merethic Era. Initially, he was believed to have been a fair ruler and successful in battle, but his mind was corrupted by unknown forces that drove him to insanity. Otar became a Dragon Priest and subjected his people to great cruelty until two Nordic heroes named Saerek and Torsten were sent to stop his tyranny
Both heroes were unable to defeat Otar, so instead they sealed him in a large sarcophagus in Ragnvald and locked it with two skull keys that each of them kept. They pledged to guard the keys so that Otar may never escape his imprisonment. The city of Ragnvald was eventually abandoned, but Saerek and Torsten remained as his guardians.
Otar can be encountered within the Nordic ruin of Ragnvald in The Reach. He is sealed in a large, locked sarcophagus in the main chamber of the ruin. Opening the sarcophagus is only possible by defeating the guardians, Torsten and Saerek, who each hold a Skull Key. Both skull keys are required to open the lock.
Upon his defeat, Otar the Mad drops the Otar Mask - one of the eight mysterious Dragon Masks located throughout Skyrim. Collecting all eight masks is a requirement for the unmarked quest to restore the Dragon Priest Shrine.