Forger's Foundry

{T}: Add {U}. When you spend this mana to cast an instant or sorcery spell with mana value 3 or less, you may exile that spell instead of putting it into its owner's graveyard as it resolves.

{3}, : You may cast any number of spells from among cards exiled with this artifact without paying their mana costs. Activate only as a sorcery.