The Shadowstalk

Also known as The Lurker or The Seeking Shadow, the shadowstalk is a common myth known all around the north that tells about a ferocious and unrelenting creature that inhabits the forests, killing the sinful and dishonorable ones that wander into the wild. It is said that once the creature sees it's victim, it will then stalk it for an indefinite amount of time, until it judges it is the right moment to attack. At the same time, the Shadowstalk is able to conceal itself completely, hiding behind trees and merging with shadows. Those that are attacked by it never return, nor leave behind any traces, as they seemingly vanish forever once taken, supposedly devoured by the being.
According to the legends, the Shadowstalk is a creature from the other realms, that somehow managed to seep into Mellanvärlden.