Slinking Giant (SHM) from Shadowmoor, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Dave Kendall
• Card Text:
  Wither (This deals damage to creatures in the form of -1/-1 counters.)
  Whenever Slinking Giant blocks or becomes blocked, it gets -3/-0 until end of turn.