People like that don't need a reason apart from "because I can". They have a nightmare and try to make it happen.
Terry PratchettCreatures which, lacking mankind's superior brain power, did not concern themselves with finding someone to blame, and instead tried to find someone to eat.
Terry PratchettMost species do their own evolving, making it up as they go along, which is the way Nature intended.
Terry PratchettThey always gives me bath salts," complained Nobby. "And bath soap and bubble bath and herbal bath lumps and tons of bath stuff and I can't think why, 'cos it's not as if I hardly ever has a bath. You'd think they'd take the hint, wouldn't you?
Terry PratchettFind the story, Granny Weatherwax always said. She believed that the world was full of story shapes. If you let them, they controlled you. But if you studied them, if you found out about them... you could use them, you could change them.
Terry PratchettTiffany knew what the problem was immediately. She'd seen it before, at birthday parties. Her brother was suffering from tragic sweet deprivation. Yes, he was surrounded by sweets. But the moment he took any sweet at all, said his sugar-addled brain, that meant he was not taking all the rest. And there were so many sweets he'd never be able to eat them all. It was too much to cope with. The only solution was to burst into tears.
Terry Pratchett