Dual Nature is a rare Enchantment card from Prophecy (PCY), collector number 112. Current market price: $2.69 (foil $22.32), TCGplayer market prices via Scryfall.
Whenever a nontoken creature enters, its controller creates a token that's a copy of that creature. Whenever a nontoken creature leaves the battlefield, exile all tokens with the same name as that creature. When this enchantment leaves the battlefield, exile all tokens created with this enchantment.