The Baldur's Gate 3 Infernal Iron item is a rare metal that you'll occasionally find in chests and treasure troves across the world. What's it for? Well, as you might gather from the name, this material plays a big part in Karlach's companion quest, The Hellion's Heart, which sees you repairing the engine in her chest.
While you should find a fair bit of Infernal Iron if you're treasure savvy, it's more comparable to Soul Coins in terms of its rarity, so it can be helpful to have a few collected already if you want to progress the quest. Here, I'll run through the Infernal Iron locations I have so far, plus who you need to see about fixing Karlach's engine.
