Real qick, I just want to note, the Forsworn aren't actually nords. They are Breton who descended from High Rock in the early years and settled the Markarth lands of Skyrim(The Reach) and when the Nords came over they forced the Forsworn into holes and caves. The Bretons of the Reach are called Forsworn because they "swore" to retake the Reach from the Nords, but they have yet to gather enough strength to do so. Their black magic, association with Hags/Hagravens, and general unwanted nature has made them target to everything from adventurers to Bounty Hunters.