Yeah, I really don't like the amount of technobabble Brandon has put in these chapters. I figured that iron and steel are not doing anything, and simply moving pieces of tin and pewter around. (You move a lever made of steel and it swaps the pewter piece for a tin one, turning the fabrial into a Diminisher from an Augmenter.)
I do hope that he swears it in Shadesmar. I think he will simply summon a ton of windspren around himself, he might also get a boost in strength.