Contest of Claws is a rare Sorcery card from The Lost Caverns of Ixalan Commander (LCC), collector number 12. Current market price: $7.15 (foil $5.80), TCGplayer market prices via Scryfall.
Target creature you control deals damage equal to its power to another target creature. If excess damage was dealt this way, discover X, where X is that excess damage. (Exile cards from the top of your library until you exile a nonland card with that mana value or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)