War Of The Twins by Margaret Weis

A time-bending fantasy in which a driven, morally conflicted mage drags his loyal warrior brother and a devoted cleric into the past as he seeks to claim the power of a legendary archmage; amid war, political intrigue, and shifting alliances they confront tests of faith and brotherhood, face heartbreaking sacrifices, and watch history—and the mage’s dark destiny—unfold with devastating consequences.

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