Dwarven Hold (5ED) from Fifth Edition, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: David Seeley
• Card Text:
  Dwarven Hold comes into play tapped.
  You may choose not to untap Dwarven Hold during your untap phase and put a storage counter on it instead.
  T, Remove X storage counters from Dwarven Hold: Add an amount of R equal to X to your mana pool.