Lava Waders

The immunity is a timer, not a permanent state. You get a window of total safety on entering lava, then you start taking damage again at a reduced rate with a shorter burn attached. Every other item in the Lava Charm family adds to that timer and they all stack, so a full loadout turns the window into long enough to strip a whole Hellstone vein. The Demonic Hellcart extends it too and is not part of that upgrade chain, which is easy to miss.

You walk on the surface of every liquid, including lava, and landing on liquid does no falling damage. Press down to sink through when you want to. That makes Hellstone mining safe from above and makes lava-based farms practical, since you can stroll across a thin layer and pick up drops that would otherwise have burned. Add a Flipper and you can swim in lava outright. The one thing that will still catch you is a liquid level changing under your feet: break a Hellstone block while standing on lava and you drop straight through the gap.

There is a wrong way to build these. Some routes burn an Obsidian Skull that a later step needs again, and one of them can waste a second. If you have already gone down the wrong path, decrafting in Shimmer is cleaner than starting from scratch. Worth knowing too: Ash Wood armor worn alongside the Waders removes lava damage and its debuff entirely, which is an odd pairing but a free one.