Mishra's Bauble

Free, but never quite free in the way the mana cost suggests. The trick is the delayed draw: you sacrifice the artifact now, peek at a library, and replace it during the next upkeep rather than immediately. That one-turn lag is what separates this from a true cantrip, and it is also what makes the card so valuable to the decks that want it. Cracking it nets you a card eventually, but in the meantime it has fueled everything that counts an artifact entering, leaving, or sitting in a graveyard: delirium, revolt, affinity-style storm counts, prowess. The peek at a library is mostly decoration; the function is to trigger those mechanics and feed the yard for the price of a card slot and zero mana. Designers have circled this idea for a long time, the zero-cost cantrip that pays for itself in graveyard count or spell count, but most attempts either drew immediately (replacing themselves at parity, with no surplus to exploit) or asked for a tax somewhere. Here the tax is hidden inside the timing: you spend the artifact this turn and recover the card next turn, and all the body of work it enables happens in that gap. The real text of the card is not the look or the draw; it is the window between when you crack it and when it pays you back, a window the rest of your deck is built to spend.