The Foundry is where your various minions will eventually work to craft defenses and constructs. The minions that are well suited to use a hammer and bellows will spend countless hours in this room as they follow the blueprints of the questionably-lucid and devilishly destructive designers to create all kinds of violent (or simply vexing) machines of war.
The torrid heat of the Foundry is the perfect environment for your mechanically minded minions to craft defenses for your dungeon. Once you've unlocked the Foundry you will be able to unlock traps within the Veins of Evil. These traps won't just appear out of thin air, Underlord, so you shall be in dire need of a minion capable with a hammer - fortunately for you the Chunder will waddle slowly to your aid, thought it will most likely laze about until your vile hand places blueprints to make your halls more perilous to those that would dare enter.
The Foundry is one of the core rooms within the Vein of Sloth.
Your minions will have the tools necessary to craft weapons and armor, granting them experience through their passive creation. The rate at which you construct defenses will also increase.