Beatrice, the Bookworm

During your turn, spells your opponents cast cost {3} more to cast.

{t}, {x}: Exile target instant or sorcery card with mana value X from your graveyard. Then create a Book token and attach the exiled card to it. (Its an artifact with "{t}, Sacrifice this artifact: Copy the attached card, cast the copy without paying its mana cost.")
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"Time to teach you a lesson, I suppose." -Beatrice.