I was thinking about the new Iron Hulk recently, and I had a few ideas on what the possible lore could be. Klei stated that it was something that was used in a war, a long time ago. And that got me thinking. Since the Iron Hulks seem more like something that was created by the Ancients, not the Pigs in Hamlet, I think that there could have been a war between the Ancients and the Hamlet Pigs a long time ago. That also might explain why the Iron Hulk absolutely REFUSES to target the Ancient Herald, due to the fact that it is likely one of the Ancients.