You have to craft it in the hall of the ice forge (i think that is the name). It is in northguard, across the river as you are going towards Mirkholm Keep.
if its from grizzleheim, use the grizzleheim craft station.
its behind the big castle once you get out of port, to the right of a big waterfall. go through the door and climb up to the hammer, it will ask you what to craft.
