My friend and I recently did the dungeon Nastrond. We killed Austri, Vestri, Nordri and Sudri, and then after the battle was completed, both of our quest logs said, "Defeat Sons of Ymir (3 of 4)." We both fled and returned one time, but we were both in the battle when all four of the brothers were (except for Sudri, whom I killed while my friend was gone, but shouldn't my quest log still say it was complete because it is a dungeon?). Is this a glitch, or a secret cheat, or...? I think I remember this happened to one of my other wizards as well.