Urza, Lord High Artificer [Modern Horizons] Island Swamp I'd have told you what

I'd have told you what it was

Set: Magic Player Rewards 2008 Type: Instant Rarity: Rare Cost: {W} Counter target spell unless its controller pays {1}

You may cast a spell from among those cards without paying its mana cost

where he discovered the remarkable Mightstone

Urza, Lord High Artificer [Modern Horizons] Island Swamp I'd have told you whatSet: Modern Horizons Type: Legendary Creature Human Artificer Rarity: Mythic Cost: {2}{U}{U} When Urza, Lord High Artificer enters the battlefield, create a 0 0 colorless Construct artifact creature token with "This creature gets +1 +1 for each artifact you control." Tap an untapped artifact you control: Add {U}. {5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.