The Kushtika, a race of half beaver, half human creatures (inspired by an Alaskan legend). Live either in the mountains or the rivers, only coming near other races villages to steal young children, which they then take back and eat..... Ya know what, this sounds more like a monster in the world. Scratch that.

Or maybe, I'll just alter it. They could live in the ocean/rivers and didn't eat people, would that be okay?