Venison Benison is a Munchkin promotional card that ties in with another game from the same publisher: Trophy Buck. It is a Treasure card worth 300 gold pieces.
To use this card, you need the dice from Trophy Buck. On your turn during combat, you may roll a die. If you roll a number, that value is added to your combat strength. If you roll the feet, you have +1 to run away. If you roll a deer, nothing happens. Once you roll a total of three deer, Venison Benison is discarded.
It's not clear whether or not you can use this ability multiple times during the same combat.