Brain Slugs
Taking over the world by controlling the thought process and actions of all, the Brain Slugs attach themselves to the top of the head of a species with the delta brain wave to feed off of its energy, as they require such a thing for nutrition. Their primary weaknesses are helmets and Garlic shampoo. They also can starve to death if the host is stupid. They've managed to establish a political base on earth as well, in the brain-slug party, which supports unreasonable subsidies to their homeworld, the Brain Slug Planet.