Surge of Strength
The trick scales off the wrong number, and that inversion is the whole idea. Most combat tricks reward sneaking your cheapest attacker through; this one keys the +X/+0 to the target creature's mana value, so the payoff grows with the size of the threat you point it at. Swing behind your biggest fatty and the boost is largest, with trample stapled on to answer the obvious counterplay of throwing a chump in front of a swollen attacker. That makes it read as a finisher rather than a margin-of-combat fixer: it does not eke out a favorable block, it pushes lethal. The additional cost supplies the balancing friction, and it is a pointed friction at that. You cannot pitch just any spare card, because the spell demands a red or green card specifically, so paying for it means feeding it a redundant creature or a spell you would rather have cast. The discard taps into the Alliances design current of hand-as-resource cards, where the question is never whether the effect is strong but whether the cards in hand are worth spending to get there. The design folds two separate levers (a colored-discard tax and a mana-value scaler) into one card, and the tension between them is what gives it character: the bigger your creature, the bigger the swing, and the more you are likely already committed to seeing the attack through.
