A Gathering of Stones — Jo Clayton

WHEN MAGIC CALLS--
not even Brann, the Drinker of Souls, can resist. And now the Chained God has drawn upon every spell at his command in a life-and-death struggle to break free of the energy-draining trap which holds him before he is driven into total dissolution. To win release from his invisible prison, the Chained God must obtain six talismans of power, and he will use Brann and the demon children, the sorcerer Maksim, and all their former allies--as well as deadly predators from another dimension--as pawns in a desperate campaign to breach the strongholds of gods, shamans, wizards, and priests, and steal the magical orbs that are the vital focal points for a magical spell more powerful than any Brann's world has ever experienced.

And should Brann and the rest fail to obtain even one of the precious talismans in time, not only will the Chained God's doom be sealed but a new and all-consuming evil will be released on Brann's own world!