Waterveil Cavern (CHK) from Champions of Kamigawa, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: John Avon
• Card Text:
  T: Add 1 to your mana pool.
  T: Add U or B to your mana pool. Waterveil Cavern doesn’t untap during your next untap step.