Their graveyard is full of nasty things and we must get rid of it
The constant stream of free spells off the top of your deck is just too much value for your opponent to deal with, and the ability to hit your opponent for 10 life with Kefka's Tower shouldnt be underestimated either
Azlask, the Swelling Scourge Eldrazi commanders with color identities are pretty new to Magic, and Azlask, the Swelling Scourge is a 5-color commander
The Emerald cards give you plenty of indirect ways to mess up your opponent's plans, meaning that this is a slow-burn deck where every play counts if you want to win
As with other board wipes, the best way to use Sunder is to pair it with a powerful creature or other threat that is capable of winning the game on its own
It's an incredible pump effect, and because it's attached to a creature and not an Instant or Sorcery, you can find it using green's excellent tutor effects