"the iron that makes up a infernal machines grows on trees, pours out of infernal fountains, floats on top of the rivers "
You're pretty close to the real world, really ... it's called Bog Iron, and it is found in swamps and bogs as a result of the natural activities of plant life. It was in fact the primary source of iron in the not-so-long-ago days. And it is renewable. I've always found bogs and swamps to be kind of magical, with will-o-wisps flitting about and the Mad Hermit living in his hollow tree, but alas, Larian is moving away from the rich landscapes of early D&D that existed long before the Forgotten Realms.
That's great! I vaguely remember some history channel-like documentary on viking swords and why they thought the swords that came from (what is now) France were magical in nature that mentioned bog iron.
You are absolutely right about the magic of bogs. I don't miss living in the midwest but one thing I do miss is seeing fireflies on warms summer nights, watching the lights dance above a dell is indeed magical experience
