Werewolves.
They say werewolves are humans until they bathe on moonlight.
They say that at full moon's night these abominations go bersek morphs into vicious beasts that feeds on man's blood and flesh. We take cautions and stay at home in fear of them at a full moon's night but think that we are safe at the break of dawn and more so in a new moon's night.
Are we really safe?
What if their human side still reigns on them even in a full moon's night?
What if the moon is just an excuse to unleash the wolves living in them all along?
They are humans, after all.
They are like us, vicious and made of greed.