Artifact of the ImmuneThis is a op way of farming "iron" because you can get revival platforms from this artifact which you can place a destroy for "iron" while not getting flak bps and a bunch of mining helmets but instead sword bps riot shields and sometimes balm. And it's super easy to farm but if you don't want to succumb to the gas then you can just craft a gas mask and then wear the gas mask after you enter the cave to prevent your health decreasing
Hope this helps you