Out of the Darkness and Into the Light
The wraith is an evil undead spirit of a powerful human that seeks to absorb human life energy.
These horrible creatures are usually seen as black, vaguely man-shaped clouds. They have no true substance, but tend to shape themselves with two upper limbs, a torso, and a head with two glowing red eyes. This shape is a convenience born from the habit of once having a human body.
The wraith has no proper niche, serving no useful purpose in nature and providing no byproducts that others can use. It requires no nourishment, killing only for the sheer hatred of life. All creatures close to nature will shun the presence of a wraith. It exists more in the Negative Material Plane than in the Prime Material Plane, and thus is not a natural part of this world.