Destroy the North Lightning Forge, the Central Lightning Forge, and the South Lightning Forge with Bouldercrag's Bombs, then return to Bouldercrag the Rockshaper at Bouldercrag's Refuge.
In my folly, I'd thought Valduran's project at Narvir's Cradle, a large construction area to the south, no more than a grotesque monument to "Keeper" Loken's cruelty.
Now we know the truth, that it was meant to be used as a weapon against us and our allies. We must not allow this iron colossus to reach completion, <name>, for it will mean the end of the refuge.
Go to Narvir's Cradle, find the lightning forges the stormforged artisans use, and sabotage them.
Were you able to hamper them by sabotaging the forges?
Excellent work! Oh, it won't stop the iron dwarves, but it'll take them valuable time to rebuild those forges. I daresay we've gained the advantage.
The three forges are all on the ground level in a line about 100 yards apart. They're more west to east than north to south, though.
-  The Earthen of Ulduar or  The Exiles of Ulduar
-  Rare Earth
-  Relief for the Fallen &  Fighting Back
-  Slaves of the Stormforged &  The Dark Ore
-  The Gifts of Loken &  Facing the Storm
While killing golems, loot the [Dark Armor Plate] to continue the quest chain.
-  Armor of Darkness
-  The Armor's Secrets
-  Valduran the Stormborn
-  Destroy the Forges! &  Hit Them Where it Hurts
-  A Colossal Threat
-  The Heart of the Storm
-  The Iron Colossus