City of Tears: Rise of the Thrall Lord Book One

Five hundred years have passed since Naradon, the mad emperor, ruled over the world of Arinthar. Unknown to all but a few, the emperor left behind a deadly legacy-seven towers scattered across the globe, each with the power to lay waste to an army.

Now demons have crawled up from the Abyss and taken one of those towers, using its power to summon more of their brethren. To make matters worse, a second tower has been uncovered and the demons want that one, too.

Yet that tower will not be taken easily. Shrouded in mist, the ancient city surrounding that tower has fallen under a terrible curse. All who once lived there walk the earth as undead, including the mad emperor's wife.

Now a small band of heroes must enter the mists and wrest the tower from the empress of the damned and her undead army. For if they fail, the entire world is doomed to become hell on earth.