The Forsworn have some old traditions from the Reachmen, the old rulers of the Reach, which are in all honesty, quite savage. When the Great War happened, the Forsworn took back control of the Reach from the Empire instead of fighting the Elves. When the Empire returned from the war, Ulfric took the Reach back from the Forsworn. The Forsworn were then almost all executed, even when it was wrong to do so, except Madanach was thrown in Cidhna Mine and "Controlled" by the Silver-Bloods. Then they started to rebel, trying to bring back their old-ways. The Silver-Bloods never had true control over the Forsworn.