Because I Have Willed It

(An ongoing scheme remains face up until it's abandoned.) Spells you cast cost {1} less to cast. At the beginning of your opponents' end step, if they cast four or more spells this turn, abandon this scheme.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6ojhk5e2xppb1h6gtsujvm.