Arriving at the fortress, the party discover that Larrel is insane, and complete a task to help him regain his sanity. Using the gem, Larrel discovers the source of the evil to reside in the former dwarven city of Dorn's Deep. Fighting their way through the city, the group eventually come across the source of the evil – a priest named Brother Poquelin (John Kassir). Poquelin reveals himself to be a demon who was exiled from his home realm by his superiors, and that both he and Yxunomei maintained a vendetta against each other that was getting out of control. Predicting she would follow him to the material plane, the demon sought a base of operation in the region to form a military force that could crush her. While doing so, he stumbled upon the ancient artifact Crenshinibon, which he claims had been "calling" to him. Poquelin immediately used its power to help him amass an army to conquer the lands of Icewind Dale, until Yxunomei's activities around Kuldahar led to the formation of Hrothgar's expedition. Seeking to stop it, the demon had his frost giant minions crush the expedition, but did not count on the adventurers' survival being a problem until they recovered the Heartstone Gem, forcing him to eliminate Arundel. Despite the party having found someone else to use it, Poquelin had managed to build up his forces, which he soon sent to Easthaven.