Death of a Demon Lord (Deluxe Edition) (2007)

From publisher blurb:

The first novel in the METAMORPHOSIS trilogy! The DELUXE EDITION - large size, full stats and game info for characters, critters, places and items, and beautiful artwork.

Death is only the beginning...

The wicked archmage Hazergal Redfist is dead, slain by the traitorous hand of his closest friend and confidant. The world rejoices as the tyrant mage's empire comes crumbling down, ending two centuries of brutal tyranny and war. But fate has only begun to weave the twisted skein of Hazergal's destiny, and as the light and warmth of life slip away, the former archmage finds himself on the bleak, demon-haunted planes of the Abyss, his soul condemned for all eternity.

Now a petitioner - the feeble soul shell from which all planar life is created - Hazergal is a shadow of his former self, seemingly bereft of the awesome power he commanded in life. Alone, defenseless, and beset by the fell inhabitants of the Abyss, Hazergal faces countless eons of torment and humiliation, his eternal reward for a lifetime of wickedness. But Hazergal soon realizes that he is different from the other abyssal petitioners. Memories of his former life remain, and in the deepest recesses of Hazergal's soul a terrible power grows, a power that will propel him along a course no mortal has ever undertaken, ultimately leading to the pinnacle of fiendish might.

But such power is a bright beacon of opportunity to the terrible abyssal rulers, and Hazergal soon finds himself embroiled in the lethal politics of the chaotic plane. Forced to emulate the demonic inhabitants of the Abyss in both body and mind, Hazergal must navigate a treacherous landscape of chaos and evil aided only by a curious rogue devil, and his own formidable intellect. And although destruction and damnation awaits him at every turn, the faint specter of ultimate power beckons Hazergal on, as he makes the arduous climb from dretch to demonlord.