Ariete da Assedio

At the beginning of combat on your turn, this creature gains banding until end of combat. (Any creatures with banding, and up to one without, can attack in a band. Bands are blocked as a group. If any creatures with banding you control are being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's blocking.) Whenever this creature becomes blocked by a Wall, destroy that Wall at end of combat.

By the time Mishra was defeated, no mage was foolish enough to rely heavily on walls.