The Water Crystal

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.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6o2y9o0wxdpb1h4rxczok8.