Curse of the Werefox is a common Sorcery card from Wilds of Eldraine (WOE), collector number 167. Current market price: $0.24 (foil $0.26), TCGplayer market prices via Scryfall.
Create a Monster Role token attached to target creature you control. When you do, that creature fights up to one target creature you don't control. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1 and has trample. Creatures that fight each deal damage equal to their power to the other.)