AKA: Troll Wraith
These trolls are normal trolls who have turned undead. They have jet black skin and hair.
As undead creatureas, spectral trolls have some remarkable defenses against normal weapons. Of course, characters trained in dealing with undead (such as most clerics) will have an easier time dealing with these creatures. They also disappear in sunlight -- this is not a form of damage, merely a cesation of existence. When night falls, they appear again in the same place.
This variety of troll wraith is sometimes said to be a kin to the invisible stalker. It fights much like a spectral troll does, but it is naturally invisible, appearing only to those with supernatural sight as an indistinct, troll-like shape. Its fangs possess the ability to heal the creature when they taste blood, and the spirit troll's claws drain an opponent's Strength, making them weak and feeble.