Speak with the Outcast Seer in The Risen Lake.
After traveling west of Welryn, you entered The Risen Lake, or at least, it used to be a lake. The living had made their homes atop raised stilts and platforms over the waters. But now, all that is left is a swampy marsh, filled with the remains of those who lived here and the walkways are filled with the forces of the Immortal Empire.
After fighting your way through the undead you have found a corner of The Risen Lake where one of the Outcasts has hidden away. She appears to be the Seer that the prisoner told you of - the one who can help you locate Alric.