Exploding Barrel is a rare Artifact card from Teenage Mutant Ninja Turtles Eternal (TMC), collector number 39. Current market price: $0.27 (foil $10.91), TCGplayer market prices via Scryfall.
{T}: Add one mana of any color. Put a pressure counter on this artifact. {8}, {T}, Sacrifice this artifact: It deals 20 damage to target creature. This ability costs {1} less to activate for each pressure counter on this artifact. Activate only as a sorcery.