Roiling Horror (PLC) from Planar Chaos, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: John Avon
• Card Text:
  Roiling Horror's power and toughness are each equal to your life total minus the life total of an opponent with the most life.
  Suspend X—XBBB. X can't be 0.
  Whenever a time counter is removed from Roiling Horror while it's removed from the game, target player loses 1 life and you gain 1 life.