Nachtheer

They are fairly certain Nacht exists, even if it hard to prove.
There are legends of long ago, before the dragons touched this land, of an unwanted child left in the winter woods. They say that instead of perishing to the cold, the child was adopted by the woods itself. Old carvings of the tale still exist, depicting a shadowy, cracked figure with a skull for a face as what became of the child.
It only took a few rumored viewings of Nacht for the connection to be made, really. His hide cracks into the deepest black and the skin on his face seems to have long since rotted away.
He's known as a force of nature, killing those lost in the woods before another element claims them. It almost seems to be a form of mercy, since it's quicker then the other options.
They say he does knows of the more traditional form of mercy though, as there's talk of another creature like him that came about when another being was left in the woods to die by those who cared for it. However, these rumors have never been proven.