Powder Keg (136) [Urza's Destiny] Grading:Near Mint you may cast that card

you may cast that card without paying its mana cost

Set: Betrayers of Kamigawa Type: Instant — Arcane Rarity: rare Cost: {X}{U}{U} You may exile a blue card with mana value X from your hand rather than pay this spell's mana cost

Set: Zendikar Rising Promos Type: Legendary Creature — Elemental Rarity: mythic Cost: {3}{G}{G} Ashaya's power and toughness are each equal to the number of lands you control

Set: Tempest Type: Legendary Creature — Elf Warrior Rarity: rare Cost: {G}{G} Other Elf creatures have forestwalk

If that mana is spent on a creature spell

Powder Keg (136) [Urza's Destiny] Grading:Near Mint you may cast that cardSet: Urza's Destiny Type: Artifact Rarity: rare Cost: {2} At the beginning of your upkeep, you may put a fuse counter on this artifact. {T}, Sacrifice this artifact: Destroy each artifact and creature with mana value equal to the number of fuse counters on this artifact.