Pool of Twilight, by James Ward and Anne K. Brown, is the final book of The Heroes of Phlan trilogy.
Summary[]
Kern, son of Shal Bal and Tarl, sets out to recover the Hammer of Tyr. The city of Phlan has greatly decayed in its absence, with many clerics of Tyr suffering, including Tarl, who went blind. He is joined by Listle Onopordum, Shal’s apprentice who is secretly an illusion come to life, Miltiades, Ren o' the Blade and his daughter Daile Redfletching, Evaine and Gamaliel, and Sirana, the daughter of the Red Wizard Markus and an erinyes who claimed her mother’s power and secretly sought the hammer for herself. Sirana is drawing power from the Pool of Twilight, a primordial chaos force that is guarded by a black dragon called Dusk, who tries to lure Sirana in to take his place. Along the way they encounter an old paladin calling himself Trooper, who trains Tarl, and Ren falls in combat with a demon. Eventually, Tarl slays the osyluth guarding the hammer, recovers it, and defeats Dusk and Sirana. Evaine destroys the pool. Miltiades is restored to life in exchange for Trooper’s and accompanies Evaine on her quest. The Hammer of Tyr is returned and Phlan begins to recover.