The Water Crystal is a rare Legendary Artifact card from Final Fantasy (FIN), collector number 85. Current market price: $3.59 (foil $5.08), TCGplayer market prices via Scryfall.
Blue spells you cast cost {1} less to cast. If an opponent would mill one or more cards, they mill that many cards plus four instead. {4}{U}{U}, {T}: Each opponent mills cards equal to the number of cards in your hand.