Floodgate is a uncommon Creature — Wall card from Dominaria Remastered (DMR), collector number 49. Current market price: $0.18 (foil $0.31), TCGplayer market prices via Scryfall.
Defender When this creature has flying, sacrifice it. When this creature leaves the battlefield, it deals damage to each nonblue creature without flying equal to half the number of Islands you control, rounded down.