Branching Bolt

The modal split here is doing the work of two cards in one slot, and the partition is the clever part: every creature on the battlefield is either flying or not, so "creature with flying" and "creature without flying" together cover the entire board with no overlap. Pick one mode and it is a clean three-damage burn spell at a slightly inflated rate; pick both and it becomes a two-for-one, dealing 3 damage to each of two separate targets as long as exactly one of them has flying. That last clause is the wrinkle that defines the card. You cannot dome two grounded blockers, so the spell forces you to spread your removal across the air and the ground, which is exactly the board state a flier attacking over a wall of dorks tends to produce. What makes the "both" mode worth playing is that it reads the battlefield rather than just pointing at one thing: it wants a two-front problem to answer at once. What you pay for that flexibility is a commitment to both red and green, plus the fact that the upside only materializes when exactly one target is airborne; against a board that is all flying or all grounded, you are buying a single mode at a premium you could have gotten cheaper in one color. It is removal built around a partition of the board, and the partition is also the leash.