Starcraft II Co-Op Mutation #126: Endless Infection
Black Death - Some enemy units carry a plague that deals damage over time and spreads to other nearby units. The plague spreads to your units when the enemy unit is killed.
Alien Incubation - All enemy units spawn Broodlings upon death.
Walking Infested - Enemy units spawn Infested Terran upon death in numbers according to the unit's life.
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Going into this game, I had no idea how to make Han and Horner work for the mutation. It seems that none of their units deal with black death particularly well, so I had to improvise.