The wraith was summoned by Sir Brightblade in an attempt to cleanse the crypt in which it was located. Instead, the Paladin was interrupted by the party and killed, so the party had to deal with the Wraith themselves. It managed to strike Bregor with a few life drain attacks, lowering his level twice before being dispatched by Vincent. The weakening of Bregor ultimately gave him more hp in the end.
It is unknown who or what the Wraith was in life, but it can be assumed that it was an evil creature.
A wraith is an undead spirit of a powerful, evil human. As such, it is usually found in tombs or places where such men and women would have died. Since such men and women are frequently buried together, in the case of the wealthy, or with their families, wraiths are most commonly encountered in packs. Those that died or were buried alone might still be encountered in packs, because a human who dies from the touch of a wraith becomes a wraith under the sway of its slayer. The treasure of the wraith is usually its possessions in life, now buried with it, or those of its victims. Wraiths exist only to perpetuate evil by absorbing the life force of as many people as possible. A character who becomes a wraith is nearly impossible to recover, requiring a special quest. The wraith cannot communicate, except through a speak with dead spell. They do not even seem to communicate with each other, except as master to slave for combat strategy. Any attempt to speak to a wraith is met with scorn, unless by a very powerful party. In that case, the wraith desires only to flee. Wraiths can be dominated by powerful evil creatures, particularly other undead, priests, and wizards, and made to serve their will.
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.