They're giant humanoids, anywhere from 3 to 15 meters tall. Their only motivation in existing is eating people. They don't have digestive or reproductive organs, and subsist on sunlight, so it's not like they need to eat, they just like to. They don't die unless you hit a certain weak spot on the backs of their necks, and they can regenerate from any injury, even losing their heads. And since they don't feel pain, nothing stops them from trying to eat as many humans as possible.