Sorcerer Redemptive (Singularity Online #6)

War has come to the Lands of Light, and the defenders of the Light look to Aranos to fight it. An army of urukkai marches on Eredain, the spider-people move against the dwarven Skollhelds, and a horde of Shadowborn descend on the Human Kingdoms. The elven capital of Cyva Alari has fallen, and the fiendish bodakkai rage freely in the forests under the thrall of the twisted, insane Traveler Lily.
The Lightborn are outnumbered and unprepared for war, their armies scattered and their lands broken and isolated. Aranos has to change that to have any chance at victory, and the key to that victory is restoring the Arcane Doors. The tendrils of Darkness run deep through the Lands of Light in the aftermath of the Feast, though, turning those who should be allies into enemies. The dark gods move openly against him, and creatures of legendary power stalk him through the Ways of Shadow.
For the Light to stand any chance at victory, Aranos must quell ancient suspicions, unite the Lightborn, and Redeem that which the Darkness Corrupted centuries ago: the Hearts of the Lands. He must travel into the Darkness and restore it to the Light - or fall to its shadow and doom the Lightborn to slavery and death.