The Infernal Furnace is a research option found under the Artifice tab, being of minor Forbidden Knowledge, and a Mystical Construct, that is inherently unlocked to research, and can be used as a "fuel free" alternative to a traditional furnace. The structure is a 3 by 3 by 3 with pillars of nether brick in the corners, a floor of obsidian, obsidian walls with iron bars on the face set to be the front, lava in the middle, and an open top with obsidian walls once again. After imbuing the structure with 50 Terra and Ignis Vis, either from a wand of other similar magical tool, the structure comes together as one large block to form the Infernal Furnace. By putting smeltable items in the top, they are spit out the front through the iron bars in the front as their finished, smelted product, along with experience. In addition to this, the furnace will occasionally give nuggets, both of meat and metal, as a free bonus, making it especially useful. Meat Nuggets can be eaten on their own to recover one point of hunger, or used to craft the Triple Meat Treat. The furnace is not entirely free, as so long as it has a source of Ignis Vis, it will run off of it. It will also occasionally produce flux. The furnace can, however, still run without a source of Ignis Vis, but it will run much more slowly. Because the process of smelting is also not instantaneous, albeit still quick when the furnace is running on Vis, one can use a Brain in a Jar to easily collect the experience ejected by the furnace and golems to collect the items as to not have to monitor it. One can fall in the top and take damage, so it is advised to be careful around the top of the furnace. However, one can put a hopper over the top of the furnace to drop items in the smelt, allowing the process to be automated by Golems if they so choose.

The crafting recipe for the Infernal Furnace, as shown in the Thaumonomicon.

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