Summoner's Bond is a uncommon Conspiracy card from Conspiracy: Take the Crown (CN2), collector number 11. Current market price: $0.13 (foil $0.88), TCGplayer market prices via Scryfall.
Double agenda (Start the game with this conspiracy face down in the command zone and secretly choose two different card names. You may turn this conspiracy face up any time and reveal those names.) Whenever you cast a creature spell with one of the chosen names, you may search your library for a creature card with the other chosen name, reveal it, put it into your hand, then shuffle.