Spectres are aggressive level ? mobs. They are summoned by Nagrorh, and will follow and assist him while he's alive.

A frightful spectre comes to you, extending his unnatural arms.>examine spectreThe ghost is dressed like some sort of ancient priest, its face paleand expressionless. From the head and down its substance slowly fadesaway to become totally transparent near the feet, making the ghostfloat softly above the ground.