Duelist's Flame

The design pins its entire payload on a phase most combat tricks ignore: the moment a blocker meets an attacker. Pumping a blocked creature is a peculiar restriction. It cannot just point at an unengaged attacker and dig for a chunk of your own library; you have to have already committed a creature into combat, been blocked, and then buy your way through with X and trample. The reward for threading that needle scales off two numbers at once. X inflates the power, and the impulse dig you take on connection is sized to the combat damage that actually gets through: base power plus X minus whatever toughness the blocker soaked up. So the block is not just a firing pin; it is a tax on the payoff, since a fat blocker eats into both the trample overrun and the depth of your dig. Overwhelm the block by a lot and you dig deep and can steal a big free spell off the top; scrape through by one and the reward shrinks with it. It reads like a combat trick and plays like a burst-value engine that happens to require a blocked attacker as its setup. That inversion (making the defender's block the setup rather than the obstacle) separates it from the long line of trample-and-pump instants that only ever ask you to be swinging into open space.