StarCraft Episode II

StarCraft Episode II: The Overmind is part of the StarCraft storyline, specifically the history of the Zerg.

Introduction
StarCraft Episode II featured the Zerg campaign after the attack on Tarsonis. In this campaign, the player took the role of a newly created (and unnamed) Cerebrate.

A Great Prize
The Zerg crushed the meager Terran resistance and laid waste to nine of the thirteen Terran worlds, including the Confederate capital world of Tarsonis.

Tassadar's forces and the Zerg battled across the core continent of the planet. However, the main Protoss fleet abandoned the Terran Sector after the fall of Tarsonis.

Meanwhile, the Zerg had acquired a chrysalis containing something very important.

Among the Ruins
The only opposition left to the Zerg on Tarsonis was a small band of Omega Squadron troops, which had been so weakened it posed little threat.

The Overmind created a new Cerebrate whose sole purpose was to protect the chrysalis. The new Cerebrate was informed that the Overmind could reincarnate it if "ever its flesh should fail."

Daggoth of the Tiamat Brood taught the young Cerebrate how to construct and maintain a hive cluster. The Cerebrate's first priority was to defeat the small band of Confederate remnants in order to prevent them from destroying the chrysalis and the hive cluster. They were located by Zasz, another Cerebrate, of the Garm Brood. The Zerg were successful. The Overmind stated, "I am well pleased young Cerebrate, and so long as my prize remains intact, I shall remain pleased. Thus, its life and yours shall be made as one. As it prospers, so shall you."

Egression
The Overmind decided to travel to Char in order to keep the chrysalis safe, but doing so required the Zerg to clear a space platform over Tarsonis of the remnants of Tassadar's forces. With help from Daggoth's Hunter Killers (specialized Hydralisks), the Protoss forces were beaten and scattered.

The Overmind created a rift into warp space, and the Zerg traveled through it to Char, a volcanic planet with many hiding places.

The New Dominion
As soon as the chrysalis arrived, it began to create problems. It had grown much larger and was creating powerful psionic emanations, directed at two Terrans - Arcturus Mengsk and Jim Raynor - for reasons that were, at the time, undisclosed.

Mengsk sent General Edmund Duke with his Alpha Squadron to Char in order to retrieve the chrysalis. Zasz was able to intercept Duke's communications and relay them to the Overmind.

Duke was faced by a fierce Zerg attack, as the new Cerebrate tried its hardest to defend the chrysalis. This forced General Duke to retreat, but he remained nearby. Daggoth ordered the Cerebrate not to pursue, as he and his Tiamat Brood would deal with the remainder of Alpha Squadron.

Agent of the Swarm
Jim Raynor was next. Taking a number of Raynor's Raiders with him, he arrived just as the chrysalis was about to hatch. The Zerg once again was able to repel the Terran opposition until the chrysalis split open, revealing the form of the Zerg's newest minion:

Infested Kerrigan, the Queen of Blades! She explained to him that she sent the psionic dreams to him and Mengsk, hoping they would come to Char and rescue her, but they weren't able to do so, and now it was too late. She quickly fell upon the Terrans but allowed Jim Raynor to escape with his life.

The Amerigo
Infested Kerrigan was created as part of the Overmind's plan to use psionic Terrans to help him conquer the Protoss. Unfortunately, her psionic power had been weakened by the Ghost conditioning she had undergone, which was so powerful it had survived the Zerg transformation process.

Kerrigan set out to solve this problem. She believed she only needed to collect information on the Ghost conditioning process to relieve her condition. This information could be found on the Terran Dominion Science Vessel, the Amerigo. Zasz was displeased by her plan, as it was risky, and if she died, the Overmind's efforts to acquire and transform her would be wasted. Kerrigan had retained the majority of her spirit, however, and ignored his advice.

Onboard the Amerigo, she was accompanied by two of Daggoth's Hunter Killers. She fought the internal security forces, defeating them and even rescuing some Zerglings that the Terrans were still experimenting on. Finally, she found the appropriate computer terminal and downloaded the information.

Battle on the Amerigo
After she left, a small number of Terran Dominion soldiers boarded the now-derelict vessel on a mission to destroy it. They were ambushed by Hydralisks, possibly Hunter Killers and fought back fiercely although it soon became clear that they would not survive any longer. Having run out of options, one soldier, out of fear, manually activated the thermonuclear charge they had which destroyed the entire ship taking both the Terrans and the Zerg with it.

The Dark Templar
Kerrigan defeated the Ghost conditioning and her powers increased. She was able to detect the presence of Protoss on the planet. Tassadar contacted her, and they agreed to a challenge. However, Zasz had detected something unusual about this Protoss, and told Kerrigan she should stay away. Again, Kerrigan would not follow his advice.

Kerrigan's forces disposed of the Protoss base, and she moved to the central arena to challenge Tassadar to single combat. Unfortunately for her, Tassadar had only left an illusion as a distraction. Tassadar told her that she was so predictable, she was her worst enemy.

The Culling
Daggoth informed Kerrigan that Zasz had died while her forces had fought with Tassadar's.

Kerrigan assumed the Overmind would reincarnate Zasz, but Daggoth told her the Overmind had been somehow paused by the strange way Zasz had been killed, and could not speak. Meanwhile, Zasz's now leaderless Garm Brood was running amok, and threatened the hive cluster.

The junior Cerebrate was ordered to use its forces to destroy the Garm Brood, while Daggoth dealt with the Protoss himself.

Eye for an Eye
With the destruction of the Garm Brood, the Overmind awoke and related some very important information. Zasz had been slain by a Dark Templar named Zeratul. Dark Templar used cosmic energies similar to those of the Overmind, and so the Overmind could not reincarnate a Cerebrate that had been killed by this method. They could also bend light around themselves, making them virtually invisible. However, Overlords were capable of sensing their presence and leading troops to attack them.

When Zeratul stabbed Zasz with his warp blade, the Overmind was able to contact his mind and read what was within. It now had the location of Aiur in a manner usable to it. (The Overmind may have learned the location of Aiur previously from absorbing the Xel'Naga it attacked; it was heading in the right direction but still didn't know the "secret" location of Aiur.)

Instead of following its original plan to send Infested Kerrigan to Aiur to help conquer the Protoss, she was tasked with hunting down and killing the Dark Templar. Kerrigan tracked down the main Protoss base on Char and surrounded the escape routes with Overlords, who could detect them. Then the Zerg moved in, destroying the base and the Protoss within. However, neither Tassadar nor Zeratul were present. Still, after this battle, the Expeditionary Fleet was virtually destroyed. Tassadar, Zeratul, and a small amount of warriors were all that remained.

The Overmind did not want to wait for its conquest of the Protoss. Leaving Kerrigan behind on Char, it created a giant warp rift and took the majority of the extended Zerg Swarm with it to Aiur.

The Invasion of Aiur
The Overmind promptly launched its invasion force onto Aiur, with the assistance of many Cerebrates, including its newest one. The Overmind's attack was not mindless, however. It ordered the new Cerebrate to acquire a Khaydarin Crystal without revealing any reason for doing so. The force that defended the Crystals, called the "Vanguard of Aiur", was much larger than the Expeditionary Force that the Zerg had fought before. Nonetheless, the Zerg defeated the Vanguard of Aiur and acquired the crystal.

Full Circle
Finally, the Overmind was willing to reveal its plan to the junior Cerebrate. It had been created by the Xel'Naga, as the Protoss had been empowered by them, and was going to add the Protoss to the Zerg Swarm as it had done to many previous species it had encountered. However, the Protoss had a powerful purity of form, just as the Zerg had a powerful purity of essence. Adding Protoss to the Swarm would give the Zerg purity of both form and essence. The Overmind felt this would make the Zerg "perfect".

In order to physically manifest on Aiur, the Overmind needed to establish itself on the spot in which the Xel'Naga first set foot on Aiur, found underneath a Protoss Temple. To do so, it needed the Temple to be cleared and the Khaydarin Crystal set in its place.

As the Temple was a very important location for the Protoss, destroying it would grant the Zerg an important psychological victory as well. Again, the Vanguard of Aiur defended this important resource, this time with help from the Ara Tribe, which acted as a reserve.

The Zerg slowly forced their way towards the Temple, destroying the Protoss defenders. As they attacked the Temple, the Ara Tribe launched its last desperate defense of it. It failed. The Zerg cleared the Temple area and implanted the Khaydarin Crystal.

Cinematic: The Invasion of Aiur
The Invasion of Aiur (Double-click for larger video) UFOwj_T2OcA Shortly afterwards, the Overmind dived upon Aiur like a bomb. The Zerg conquest of Aiur had begun.