Rock Slide

The X-damage split looks generous on paper: spread the damage across as many attackers or blockers as your mana can buy, picking the assignments at instant speed once combat math is locked. But every clause narrows the window. It only reaches creatures that are attacking or blocking, so it does nothing to a creature sitting back; it ignores fliers entirely; and it cannot touch a player or a planeswalker. That fences the card into a single job: punishing an overextended ground assault, or wiping a wall of chump blockers, in the one phase where the targeting requirement is satisfied. The instant timing is the whole point, since it lets you wait until blocks are declared and then carve up the board with full information, turning a wide attack into a sweeper aimed precisely at the creatures committed to the dirt. It is a design that trades flexibility for efficiency: the more conditions you accept, the more damage your mana buys, and a player who builds their turn around the combat step gets a divided burn spell at a rate open-ended burn rarely offers.