Creeping Tar Pit (NCC) from New Capenna Commander, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Jason Felix
• Card Text:
  Creeping Tar Pit enters the battlefield tapped.
  T: Add U or B.
  1UB: Creeping Tar Pit becomes a 3/2 blue and black Elemental creature until end of turn and can't be blocked this turn. It's still a land.