Lurker-in-Light

This large-eyed humanoid looks like a glowing, emaciated elven child save for its small, transparent wings. A lurker in light is 3 feet tall, but weighs only 20 pounds.
Malicious and alien fey, lurkers in light venture to the Material Plane to perpetrate strangely targeted mischief, stealing and killing according to a logic or system of justice only they understand. Gnomes in particular seem to incur these unexplained attacks, leading some to believe that lurkers may be agents of ancient and vengeful forces. Creatures of the light, lurkers are visible only in dim illumination, with anything brighter than a flickering torch making them completely invisible, even as they savage their enemies—a prospect terrifying to those civilized races that equate light with safety.
A lurker in light turns conventional wisdom on its head, for they detest darkness and the creatures that dwell in it, yet they themselves are sadistic and evil. They particularly hate darkmantles, dwarves, and creatures from the Plane of Shadow, and given the time, they enjoy torturing such creatures to death if they can capture them alive.