Boethiah, the Daedric Prince of deceit and conspiracy, utilizes avatars to impose her will upon the world. These avatars, always tricky and often unpredictable, can appear as males or females, Dark Elves or some other race. They usually insert themselves into important or momentous events, working behind the scenes to drive such events to a conclusion that serves the will of their secretive master.
Avatars of Boethiah often issue challenges and trials intended to test the mettle of worthy heroes and common folk alike. Their motivation is never clearly stated and usually obfuscated, but are always assumed to be a part, either small or large, of the greater machinations of their master.
When these challenges and trials come to an end, usually when the task assigned by the masked avatar is accomplished, it is common for the avatar to disappear without a trace. This often leads to mysterious stories, strange legends, or, at the very least, a level of confusion among those who participated in the challenge.