YMMV / Unholy Grail

• Complete Monster: The demon who takes the true Merlin's name and skin intends to amuse himself by driving England into ruins. Locating the infant future King Arthur, Merlin massacres those who know of him and slowly corrupts the boy into a supposedly-noble king who brutally unites the land via bloody conquest and massive bloodshed. Upon his marriage to Guinevere, Merlin engineers her kidnapping, murdering his pawn there, and tricks Guinevere into adultery with the heroic and noble Lancelot, creating a homunculus known as Morgana from Guinevere's lusts. Merlin then attempts to have Guinevere burned alive—not telling Morgana this will kill her as well after she'd seduced King Arthur. When Guinevere is pregnant, Merlin uses his magic to murder her child to give Morgana's, Mordred, life, and later manipulates Mordred into taking over as a tyrant for the sheer amusement of watching Arthur's civil war against his own son, mocking Guinevere for his actions even as he kills her and Morgana. A depraved creature seeking only to alleviate boredom, Merlin endlessly seeks to corrupt those around him to entertain himself with the ensuing chaos.