16+ Iron Door Key. This is the easier way to get to. Bloodborne where to use iron door key in nightmare of mensis.
You will need three keys to open it. It is looted from guard mol'dar. Beautifully designed, this knocker will stand out.
You could access it by 2 blocks if you throw the key to an iron door.
Now place a redstone torch as shown. This locked door is found in the temple of miraak sanctum in the same chamber where you learn the dragon aspect shout. Of the three great bridges that link the two cathedral cradles, this key opens the iron door that leads to the midlevel bridge. From 81 manufacturers & suppliers.