Invisible Stalkers

These deceitful beings use their invisibility to sneak on their foes and strike them down from behind; however, apart of the obvious problem of being somewhat difficult to spot, they are not very strong. Usually, the only parts visible of them are their red glowing eyes, but their outlines flash when hit.

They are found in the Plateau (and possibly elsewhere nearby).

Notable examples
In a cave on the Plateau, invisible stalkers guard a big door. It is speculated that would have been the door to The Lost Vale.