The Dwarven god, feeling that his people should work towards a path of redemption, feels that the new Party is the perfect tool for his choice. None of them are dwarves so they bear none of the taint, but they are in the right place at the right time to be 'Geas'd' to seek knowledge. They are sent to an Oracle in a hard to get to out of the way place where they are tasked with going to seek some sort of connection to the original party. Once this is received, they gain an ability to draw the evil out of the tainted dwarves left in the ruins of the capital and they must work their way lower and lower in the glass/mirror ruins and higher and higher into the twisted hierarchy of the new dwarven lords there... to redeem a people to their god.