Moon of the spider - Richard A. Knaak

Driven by nightmares to the ruins of a forgotten realm, Lord Aldric Jitan uncovers the entrance to a mysterious tomb, where an ancient, dormant evil awaits the proper celestial moment to return to the mortal plane. With no other help available, the Necromancer Zayl, a servant of light in eternal struggle for dominance between heaven and hell, attempts to stop the encroaching darkness alone...until he learns that one of his own order is bringing about the return of the spider demon Astrogha, in order to restore a cosmic balance which may have tipped dangerously on the side of the angels.