Joint Assault

A one-mana +2/+2 at instant speed is respectable body math on its own, roughly Giant Growth's shift folded into a trick rather than a straight pump. The conditional clause is where the design gets interesting: if the target is paired with another creature, that partner gets +2/+2 too, so a single green mana can swing four power across a combat step the opponent has to read off the stack with no way to split the difference. That conditional is also the whole tension, because the card is built to reward a board it cannot create by itself. It needs the pairing already established, which ties it to a deck committed to soulbond rather than one splashing generic combat protection. The timing math cuts sharply against the caster. Because the spell targets exactly one creature, a removal spell pointed at that target before Joint Assault resolves leaves the trick with no legal target: it fizzles entirely, delivering neither the doubled buff nor even the base +2/+2. The bonus for the partner is not a separate target, so if the partner is the creature that dies, the spell still resolves and grants its full +2/+2 to the survivor, minus the doubling that no longer has anywhere to land. The payoff is fragile precisely where you want it strongest, at instant speed with two bodies committed. Off a paired board it is a slightly overcosted single-target pump, a card that lives and dies on whether its archetype ever came together.