Use a Tamed Jormungar to defeat the Iron Colossus and return to Bouldercrag the Rockshaper at Bouldercrag's Refuge.
We have failed to prevent the completion of the iron colossus, [player], which means we have no choice but to face it in battle.
Bruor has devised a plan to exploit the colossus' only weakness.
No matter how tough the colossus' armor is, it is still vulnerable to acid. Bruor's men have captured and trained a number of adult jormungar. Take control of one using the orbs along the northern edge of the Snowdrift Plains, then search the plains for the colossus and use your jormungar's acid breath against it.