I found one in the room to the left of the staircase near Alutiiq, and one at the back behind the iron gate. I checked chest in the left room, and it was locked, After the fight, i opened the chest, but it only contained a health potion and some gold, i reloaded an earlier save, and tried again, this time it was a strength potion and some gold. I tried opening the locked chest before the fight, and i was actually able to pick the lock, so i assumed that wasnt the chest that the key opens. Is this a bug perhaps, if so, i dont know what to do to work aroudn this