Mikaeus, the Unhallowed is an expensive but really cool card to include if you can. For 3 generic and 3 black mana he is a 5/5 Zombie Cleric with Intimidate, “Whenever a Human deals damage to you, destroy it,” and “Other non-Human creatures you control get +1/+1 and have undying.” He is a good target for mutating but even more than that he protects our strategy really well by giving all of our creatures Undying. When a creature with undying dies, if it had no +1/+1 counters on it, you get to return it to the battlefield under its owner’s control with a +1/+1 counter on it. The reason this works great with our mutate strategy is that when one of our stacks of 2 or 3 mutated creatures dies, then ALL of them will come back separately and with a +1/+1 counter on each of them! This can make your opponents hold back board wipes like Wrath of God and make your board wipes like Deadly Tempest nearly one-sided.