Ultralisk evolution

Ultralisk evolution is an evolution mission available in StarCraft II: Heart of the Swarm.

Mission
During the Battle of Korhal, Abathur located a Terran Dominion research facility called Metis, which was experimenting on ultralisks. Sarah Kerrigan took control of a specimen in the facility and began a rampage, eventually freeing more ultralisks. The power backlash from destroying the power source to their containment cells ruptured nearby holding tubes containing a toxic compound. Abathur bonded the compound to the ultralisks, creating the noxious strain. The enhanced ultralisks continued their attack, freeing additional specimens and ultimately escaping the lab.

On the outskirts of Augustgrad was a Dominion military supply center that was testing experimental nuclear weapons. A number of ultralisks approached the facility, and Arcturus Mengsk ordered one of the experimental nukes fired on them. The nuke did not kill the ultralisks, but Abathur analyzed the radiation left by the impact and used it to revive an abandoned evolutionary path of the ultralisk breed - the torrasque strain. Mengsk continued to order nuclear strikes on the facility's grounds, but the regenerative abilities of the torrasques allowed them to push to the facility itself and destroy it.

Gameplay and Walkthrough
In the first part of the mission, the player will command a lone ultralisk against a handful of marines before freeing two more ultralisks, at which point all three mutate into the noxious strain. These three ultralisks must then advance through large numbers of Dominion forces to escape the lab. Pausing to allow the cooldown for their ability to reset is advised to maximize their damage output. It is possible one of the ultralisks may die, but two will likely be enough to complete the mission in spite of the loss.

In the second part of the mission, the player receives control of three ultralisks. Upon attacking the Dominion defenses a nuclear warhead will fire upon them, and they will mutate into the torrasque strain. The bridge will then extend to allow access to the path to the facility. More warheads will fire on the torrasques, likely killing them, but they will quickly regenerate. Upon reaching the facility more ultralisks will be given for the final attack. When the facility is destroyed and its defenders dead, the mission ends.