The 109th Division

The quest text doesn't really explain the purpose of the "Shadowforge Lock" in the design of the dungeon. The lock is the locking mechanism on a huge wheel. (To find the lock, look for the overhead wheel inside the garrison -- see screenshot.) The wheel is apparently connected, via a chain, to one of two massive doors across the Dark Iron Highway. Activating the Shadowforge Lock lowers it, allowing the wheel to spin and the door to close. Having both doors closed would stop any invaders trying to enter Shadowforge City via the Dark Iron Highway. Also, passageways built inside the doors would align with each other and with ones in the surrounding rock walls. Defenders could then use these passageways to cross as needed between the East and West Garrisons. They also could shoot down from windows and platforms along the passageways at any invaders that were attacking the doors.

When you first enter the instance, the eastern door is partially open so the passageways don't line up. As a result, you you can only get as far as the upper door hinge on the east side. You can look through a gap there, but you can't get inside the door until you unlock the wheel and the door closes. If you go down to the highway first and look up at the other edge of the door (or look carefully at the dungeon loading screen), you can clearly see the other end of the passageway through the east door. You can also see the windows in the garrisons and the defensive platforms on the doors from the highway.

Once the east door is closed, you can cross the highway and reach the West Garrison and the parts of the dungeon beyond it (including the Grim Guzzler) but you won't be able to walk up the Dark Iron Highway to the Dark Anvil or [npc=9017] anymore. They can still be reached by going down through Shadowforge City or jumping down, though.

Personally, I think the locking mechanism and doors are a neat features and I think it's a shame that so few players appreciate what the instance designers hoped to convey with them. BTW, Dark Iron Tacticians is the equivalent quest for Alliance players.

I had some substantial trouble with this as well. But, after a few hours of cursing and pulling my hair I got it. So, just in case there will be more of us that don't see it at first, here goes. In the very first room you enter after accepting quest you will find some mobs and most importantly The Shadowforge Lock. Do not go up the stairs, clear the room and you will see it, it is right in the middle. The Shadowforge Lock is a quite big doohickey so you might not think of it at first. I have submitted a screenshot of the lock as well for those that might not get my otherwise brilliant explan

Hierophant turn in is a bit tricky. Just hiding just off to the right hand side in her own alcove precisely at the entrance to the Grim Guzzler. Once you cross the bridge from the Manufactory, she is just before the ramp that leads into the bar proper.