Jeleva, Nephalia's Scourge

Flying When Jeleva enters, each player exiles the top X cards of their library, where X is the amount of mana spent to cast Jeleva. Whenever Jeleva attacks, you may cast an instant or sorcery spell from among cards exiled with Jeleva without paying its mana cost.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6o619h3dqppb1hlikkqy7d.