Specter

A specter is the angry, unfettered spirit of a humanoid that has been prevented from passing to the afterlife. Specters no longer possess connections to who or what they were, yet are condemned to walk the world forever. Some are spawned when dark magic or the touch of a wraith rips a soul from a living body.
When a ghost’s unfinished business is completed, it can rest at last. No such rest or redemption awaits a specter. It is doomed to the Material Plane, its only end the oblivion that comes with the destruction of its soul. Until then, it bears out its lonely life in forlorn places, carrying on forgotten through the ages of the world.
Living creatures remind the specter that life is beyond its grasp. The mere sight of the living overwhelms a specter with sorrow and wrath, which can be abated only by destroying said life. A specter kills quickly and mercilessly, for only by depriving others of life can it gain the slightest satisfaction. However, no matter how many lives it extinguishes, a specter always succumbs to its hatred and sorrow.
Sunlight represents a source of life that no specter can ever hope to douse, and it pains them. When night falls, they leave their final resting places in search of living creatures to slay, knowing that few weapons can harm them in return. At the first light of dawn, they retreat back into the darkness, where they remain until night falls again.
A specter doesn’t require air, food, drink, or sleep.