Izzet Leyline Aggro floods the board with cheap creatures (Elusive Otter, Stadium Headliner, Slickshot Show-Off) and pumps them with Ancestral Anger and Wild Ride, so Split Up is a strong sweeper against their tapped attackers or their untapped blockers depending on the board. Twinmaw Stormbrood is too slow at 6 mana against this fast aggro-mirror matchup, so we cut them for a cheap wipe.