The Hero of Ages

Tricked into releasing the evil spirit Ruin while attempting to close the Well of Ascension, new emperor Elend Venture and his wife, the assassin Vin, are now hard-pressed to save the world from Ruin's deadly Inquisitors, the insidious lethal mists called the Deepness and the increasingly heavy falls of black ash that threaten to bury the land and starve its inhabitants