If you know Jack Chalker you know this book.
People living on a strange world with strange powers to force their will on living bodies. In a war against demons that have been locked out for millions of years, but someone wants to open the front door.
Mervyn, wizard and Fluxlord, leader of the Nine Who Guard, faces the ultimate threat of the opposing Seven Who Wait: the opening of the Hellgates to World. Closed more than two thousand years ago, they are portals to unknowable danger and, perhaps, great power. Mervyn must gather the shattered forces of guardianship, dispersed and reeling after the battle with Coydt: Cassie, once the powerful saint and crusader, now the brainwashed slave of an oppressive male dictatorship. Spirit, her daughter, controlled by her mysterious Soul Rider. Jeff, Spirit's son. Matson: he will lead the entire force of the Stringers Guild to war, if need be. But all of them are doomed to death unless they can become Masters of Flux and Anchor.
Soul Rider Book Three....Mervyn, wizard and Fluxlord, leader of the nine who guard,faces the ultimate threat of the opposing seven who wait: the opening of the hellgates to world. but all of them are doomed to death unless they can become MASTERS OF FLUX
Note: Soul Rider Three, Masters of Flux & Anchor. First printing Jan 85 has a variation in the cover.