Fire Navy Trebuchet is a uncommon Artifact Creature — Wall card from Avatar: The Last Airbender (TLA), collector number 100. Current market price: $0.22 (foil $0.28), TCGplayer market prices via Scryfall.
Defender, reach Whenever you attack, create a 2/1 colorless Construct artifact creature token with flying named Ballistic Boulder that's tapped and attacking. Sacrifice that token at the beginning of the next end step.