Tide of War is a rare Enchantment card from Champions of Kamigawa (CHK), collector number 194. Current market price: $1.57 (foil $6.52), TCGplayer market prices via Scryfall.
Whenever one or more creatures block, flip a coin. If you win the flip, each blocking creature is sacrificed by its controller. If you lose the flip, each blocked creature is sacrificed by its controller.