We all know that angry Demons inside furnaces like to set make loud noises, set things on fire, and teleport blocks around because they're angry. But what happens if you try to smelt a demon with another demon? Well, that makes it way worse. The range of the bad effects is now 15x15, from bedrock up to the sky limit. And the smelting never finishes. And sometimes the blocks teleport into the furnace itself... hey wait, isn't that a quarry?
Yes, that is a quarry. It makes a horrible mess of the landscape and makes you wish you would turn your sound off.
Just like demon-powered smelting, tile entities aren't affected, so you can use chests and Demon Item Movers to get the items outside of the blast radius.