Koskun Falls [Homelands] Magic 2011 you may sacrifice an artifact

you may sacrifice an artifact

Whereas Mishra works in metals and stone

If that mana is spent on an instant or sorcery spell

but my host would casually push it down before I could make out what it was

Set: Amonkhet Invocations Type: Instant Rarity: Mythic Cost: {3}{U}{U} You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost

Koskun Falls [Homelands] Magic 2011 you may sacrifice an artifactSet: Homelands Type: World Enchantment Rarity: Rare Cost: {2}{B}{B} At the beginning of your upkeep, sacrifice Koskun Falls unless you tap an untapped creature you control. Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.