The Seventh Gate

Description for THE SEVENTH GATE by Margaret Weis & Tracy Hickman:

Mortally wounded, Haplo finds himself at the mercy of Lord Xar, facing a fate worse than death. Xar plans to resurrect Haplo--bringing him back to life as one of the tormented living dead--to force him to reveal the location of the legendary Seventh Gate. In Haplo's darkest hour, the only hope for his rescue lies with Marit, Hugh the Hand, and Alfred.

But a terrible decision awaits them: To save Haplo they must enter the forbidden Seventh Gate. If they do so, they risk betraying its location to Lord Xar, who will use it to claim his terrible dominion over the worlds. Suddenly all their lives--and the fate of the sundered realms--hang in the balance. The final chapter is about to unfold in the apocalyptic struggle between good and evil....

This is #7 in The Death Gate Cycle Series.