Arcane Savant

The whole machine runs on a step most cards never touch: before you shuffle, it lets you set aside an instant or sorcery you drafted but cut from your forty, exiling it as a payload the body can detonate later. That splits deckbuilding into two tiers. The maindeck is the floor; the picks you made and chose not to run become a hidden reserve, and when the creature lands it copies one of them and casts the copy for free. It cares about the physical pool you assembled during a draft rather than the cards in your library, which makes it inert anywhere that pool does not exist and impossible to grade by its rate. The free cast is what justifies a 3/3 with no other combat relevance: you are paying a body and a tempo hit for a tutored, mana-free spell of your choosing, plucked from cards you already own this game but kept off the page. What stops it from being a blank check is the requirement that you drafted something worth exiling and then declined to maindeck it. That rewards greedy picks over lean ones, since the engine is only as good as the surplus you hoarded. It exists because its environment lets a card reach back into the picks you made and never played.