Form of the Dinosaur is a rare Enchantment card from Rivals of Ixalan (RIX), collector number 103. Current market price: $0.31 (foil $0.29), TCGplayer market prices via Scryfall.
When this enchantment enters, your life total becomes 15. At the beginning of your upkeep, this enchantment deals 15 damage to target creature an opponent controls and that creature deals damage equal to its power to you.