Warcraft®: The Last Guardian
Written by Jeff Grubb.
The Guardians of Tirisfal: a line of champions imbued with godlike powers, each one through the ages charged with fighting a lonely secret war against the Burning Legion. Medivh was fated from birth to become the greatest and most powerful of this noble order. But from the beginning a darkness tainted his soul, corrupting his innocence and turning to evil the powers that should have fought for good. Torn by two destinies, Medivh's struggle against the malice within him became one with the fate of Azeroth itself...and changed the world forever.