Synthesis Pod

Cast-your-opponent's-cards effects usually work off the graveyard or off the top of the library at random, but this one uses your own spells as a tuning dial. Exile a spell you control, and you dig into an opponent's deck for a card worth exactly one more than what you gave up, then cast it for free. The mana value equation is the whole engine: it converts a known input (the spell you exile) into a targeted theft one rung higher on their curve, so the payoff scales with what you feed it. Exile a two-drop, hit something worth three; feed it a bigger spell and reach deeper into their threats. The Phyrexian mana on the activation keeps the ability ticking when your blue is scarce, paying with life to sustain the loop. What balances it is the resource tension baked into every activation: you are spending your own spells to steal theirs, and the spell you feed in is gone for good, so each use is a genuine trade rather than open-ended value. That pushes deckbuilding toward a stock of expendable cheap spells kept specifically to convert into an opponent's expensive ones, a different axis than most theft artifacts ask for. The randomness in which card you hit is the concession that stops a one-for-one-plus-a-tier from being oppressive: you choose the price and the tier, but not the prize.