Shellshock (TMC) from Teenage Mutant Ninja Turtles Eternal, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Brandon L. Hunt
• Card Text:
  For each opponent, choose up to one target creature that player controls.
  Shellshock deals X damage to each of those creatures. You create a Mutagen token for each creature dealt damage this way. (They're artifacts with "1, T, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")