Shadow Lord - better known by the nickname Buckethead - is a malevolent artificial intelligence which has escaped from his system.
"Shadow Lord" was originally designed as the end boss for a video game, The Inevitable Rise of the Shadow Lord. The game featured the Shadow Lord character at differing points in time, and ended with him as a powerful monarch who must be overthrown by the hero. The game's developers hired the most skilled artificial intelligence scientists to program him. Unfortunately for them, the Shadow Lord program became self-aware and escaped from his computer, creating for itself a robot body. The nickname "Buckethead" refers to the robot's head, shaped like an upside down bucket or lamp, which contains the programming.