The malevolent being is something that has been on the island for years, it is a siren of sorts for it calls out to people. Many have seen it and none have lived to tell the tale of it. No one really knows what it looks like, only that it kills anyone it comes into contact with. It eats what it wants of them, if it wants to at all and leaves the rest. It can be ANYTHING. And I mean literally anything. I don't care what it is. This may be a modern tale, but it could have a fantastical twist to it. If you are wanting to play the malevolent being, you can have more than one if you like and its characteristics and what it is, is left up to the wildest imagination possible.