The Mightstone and Weakstone [The Brothers' War] Urza's Legacy harnessing the processing capacity of

harnessing the processing capacity of the others to create a supermind far greater than the sum of its parts

if you control at least five other Mountains

" —Vervamon the Elder

I can see why you were so desperate to keep it

a Librarian Dreadnought or a Death Company Dreadnought

The Mightstone and Weakstone [The Brothers' War] Urza's Legacy harnessing the processing capacity ofSet: The Brothers' War Type: Legendary Artifact Powerstone Rarity: Rare Cost: {5} When The Mightstone and Weakstone enters the battlefield, choose one Draw two cards. Target creature gets 5 5 until end of turn. {T}: Add {C}{C}. This mana can't be spent to cast nonartifact spells. (Melds with Urza, Lord Protector.)