Mourner's Surprise is a common Sorcery card from Outlaws of Thunder Junction (OTJ), collector number 94. Current market price: $0.18 (foil $0.23), TCGplayer market prices via Scryfall.
Return up to one target creature card from your graveyard to your hand. Create a 1/1 red Mercenary creature token with "{T}: Target creature you control gets +1/+0 until end of turn. Activate only as a sorcery."