Once again, Stoneheart had to take his burden across, or rather underneath, an ocean. It would be the tool to some dirty work, but it had to be done. Oneye had gone to far, and the Spirits were in agreement on ending the threat , if not on how to do it.
The Arcane from the West would have to find some muscle locally. He would not risk his own dwarves on the task. The were valuable to him and their sense of self-righteousness could prove inconvenient. No, he would have to find powerful allies in the North who did not fear to do what had to be done by any mean necessary.