just to clarify, the twisted rune has nothing to do with any quest. it might have had, if the makers had had more time...rumors are, that it was going to be one of the biggest, if not
the biggest quest, aside from the main quest. You do get a sweet staff from the encounter, and the encounter is moderately challenging, at least for the first time. Calsiumus has already stated that you need a rogue stone to pass through the door in the bridge district, so i wont have to tell you that