The Evil One is one of the main antagonists of the horror-based video-game Waxworks and was one of numerous "evil" twins that plagued the in-game universe due to a complex curse spanning centuries.
The Evil One was a dark priest of a chaotic cult that practiced [theistic] satanism and black magic. Whilst in prayer to his terrible master, he was give the recipe for a magical formula that enslaved humans to the Evil One's will whilst making them physically superior to other humans. Prolonged use of the formula began to tell on the bodies of the Evil One and his disciples who gradually transformed into hideous mutants becoming more and more plantlike with every dose. Eventually they could no longer go unnoticed in the world of men and they were forced to move their base of operations to a nearby abandoned mine near an unsuspecting small village.
By this time the Evil One had become so deformed that he could no longer walk and was forced to reside in a rotten stagnant pool where he was fed fresh victims by his followers. They took the innocents from the local community subtely so as not to arouse suspicion and went unnoticed for a long time. Gradually, a large number of people were force fed the elixir and bent to the Evil One's will.
Eventually the Evil One was defeated when the last "good" twin went back in time and aided some surviving soldiers in the mine, supplying them with dynamite by which to destroy the mine and bury the evil creature along with many of its followers.