The mask is the titular object in the game The Legend of Zelda: Majora's Mask. The device was apparently fashioned long ago, by an ancient tribe of peoples who attempted to weild it's power for their own use. The underlying nature of the mask, however, corrupted any that would wear it. The tribe, worried it might be used to enact something terrible, sealed the mask away hoping to stop anyone from falling victim to its corruption and becoming a conduit for it's power and malice.
In The Legend of Zelda: Majora's Mask, the artifact is once again loose in the world, the tribe having long vanished. It finds itself in the possession of the Skull Kid, a mischevious entity, who stole it from a traveling mask salesman. How this man came to hold the mask, and more importantly not be affected by it, is unknown. Through the Skull Kid, Majora's Mask attempts to bring about the destruction of Termina (the land in which the game takes place), warping him and emphasising his less desirable character traits.