Hellforge

A Hellforge is a type of Furniture that incorporates the same functions as a regular Furnace and allows you to smelt Hellstone into Hellstone Bar

It is found in The Underworld or rarely dungeon and can be picked up with a Hammer, or by destroying the blocks below it.

In patch 1.0.4 a Hellforge above the rock layer can be moved with any hammer, but Hellforges in the Underworld still requires a 60% power hammer or stronger (meaning you need either a Meteor Hamaxe or a Molten Hamaxe).