Dominions/YMMV


 * Complete Monster: Where to start...
 * The Melqart Kings of Hinnom, who not only practice Blood Magic, but devour their own people and even their own offspring, a trait they inherited from their Nephilim ancestors.
 * The Blood Fountain pretender, who demands that little girls be blinded to serve as its mouthpiece.
 * Blood nations in general. They sacrifice hundreds of innocent virgins to demons in exchange for the destruction of their enemies.
 * R'lyeh. The Aboleths are "merely" psionic alien slaver lords from the deep sea, who overwhelm the minds of the other aquatic races to build their ancient cities. The Illithids who replace them are terrifying beings from beyond the stars who plumb the depths of madness and will plunge the world into an endless nightmare ruled over by their Pretender.
 * Moral Event Horizon: Casting Burden of Time. In-Universe it's perhaps the vile spell that avalable to players. Out of universe, setting it off during a multi-player game is a sure-fire way to get everybody (aside from the AI) to gang up one you.