Wild Pair is a rare Enchantment card from Conspiracy: Take the Crown (CN2), collector number 196. Current market price: $1.45 (foil $3.25), TCGplayer market prices via Scryfall.
Whenever a creature enters, if you cast it from your hand, you may search your library for a creature card with the same total power and toughness, put it onto the battlefield, then shuffle.