Black Widow, Super Spy

The forced choice is the whole engine, and it is a genuinely sharp piece of design. Combat damage doesn't just steal a card off the top of the defender's deck; it exiles cards down to the first nonland and hands you a decision between two very different payouts. Take the counter and Black Widow snowballs into a bigger evasive threat, easier to connect with next turn thanks to menace. Decline it and you get to cast the exiled spell, still paying its cost but with mana of any type, which turns an aggressive two-drop into a repeatable theft that ignores the defender's colors entirely. The tension is that both options feed the same clock: the counter makes the attack land more reliably, and the exiled spell converts a landed attack into resources, so neither line is strictly better. What separates this from prior top-of-library theft is that mana clause. Older effects that grabbed the top card of a deck usually stapled you to whatever colors you'd already assembled, so a stolen off-color bomb sat there uncastable. Letting any type of mana pay the cost means the exiled card is functionally always castable, whatever it happens to be. Menace on a two-power body is the delivery mechanism: cheap enough to hit early, awkward enough to block that the trigger fires more often than a lone blocker would suggest. The result is a small aggressive creature whose real threat is not its two damage but the accumulating decision it forces every time it connects.