Spawning Pool (10E) from Tenth Edition, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Nils Hamm
• Card Text:
  Spawning Pool comes into play tapped.
  T: Add B to your mana pool.
  1B: Spawning Pool becomes a 1/1 black Skeleton creature with “B: Regenerate this creature” until end of turn. It's still a land. (If it regenerates, the next time it would be destroyed this turn, it isn't. Instead tap it, remove all damage from it, and remove it from combat.)