Psionics

Psionics was the psychic power that ran through all three of the galaxy's dominant species and shaped much of the history of the Koprulu sector. Among the protoss it was the foundation of an entire civilization, expressed through the communal link of the Khala and the shadow energies of the Void. Among the terrans it was a latent gift that left them only a few steps from becoming a formidable psionic power, and which made them valuable to the zerg. For the Swarm, psionics was both the medium of its communication and the means by which it was controlled. (StarCraft (manual); StarCraft)

Psionics among the protoss#

For the protoss, psionics was not a rare talent but the basis of their nature. All protoss eyes glowed with latent psychic power. Their psionic abilities ran further than those of terran ghosts: they were natural mind-readers who had to learn to filter the thoughts of others and to block and release their own minds, and they could think through many lines of thought and memory in the span of a second. Some feats, such as the creation of shields, could be performed without technological aid only by a small minority. (StarCraft II: Nature of the Beast; StarCraft: The Dark Templar Saga: Firstborn; StarCraft: The Dark Templar Saga: Shadow Hunters; In the Dark; StarCraft (manual))

Protoss communicated psionically, either through emotionless "speaking" or through the nerve cords that carried emotion and formed their racial gestalt. They spoke a mental language, Khalani, in telepathic bursts, and could even interface directly with terran video systems. Psionic power also tied the protoss to their dead: through the Khala, and with the help of the Templar Archives, a protoss could sense the memories and experiences of fallen warriors, though only preservers held full access to this knowledge. (StarCraft: The Dark Templar Saga: Firstborn; StarCraft: The Dark Templar Saga: Shadow Hunters; StarCraft Field Manual; StarCraft (manual))

The Khala and the Void#

Protoss psionics flowed through two great channels. The Khala, founded by Khas at the end of the Aeon of Strife, was a communal link that bound its adherents in shared emotion. Its discipline was required to control the most dangerous abilities, the psionic storm chief among them, and long after the Strife the untrained rogues who would become the Nerazim inadvertently unleashed such storms on Aiur when they could not control their powers. Its fortitude protected its followers from assimilation by the zerg. (StarCraft (manual); StarCraft: The Dark Templar Saga: Shadow Hunters; StarCraft: Frontline Volume 2)

The Nerazim, having severed their nerve cords and cut themselves off from the Khala, drew their psionic energies from the Void instead. These shadow energies were harmful to the zerg cerebrates and the Overmind because of the similarity of the cosmic forces they wielded, and the Dark Templar regarded their powers as the protoss' true gifts, wider than the narrowed power of the Khala. Their abilities included what was described as bending light and merging with shadows, the cloaking craft that Adun had taught them. Wielding the Void and the Khala simultaneously granted a protoss incredible power but risked burning them out like a star, and only a few, among them Adun and Tassadar, could do it. (StarCraft; StarCraft (manual); StarCraft: The Dark Templar Saga: Shadow Hunters; StarCraft II: Legacy of the Void)

Terran psionics#

The terrans were a young species, physically inferior to the elder races, but they carried psionic potential and stood only a few steps from developing into a formidable psionic power. That potential could be measured, refined, and weaponized: the Terran Confederacy experimented with psi emitter technology during the Great War, and the Sons of Korhal later used stolen psi emitters to lure the zerg to Tarsonis and destroy the Confederacy. The most powerful terran psychics, the ghosts, wielded telepathic and telekinetic abilities, while weakly psychic terrans called wranglers were employed to seek out other psychics. (StarCraft (manual); StarCraft; StarCraft: Ghost: Nova)

It was the terrans' psionic value that first drew the zerg to them, for the Overmind ordered the assimilation of the species precisely because their psionic potential was needed to fight the protoss. One terran, Sarah Kerrigan, was a ghost of exceptional power whose psionic strength the Swarm sought to claim when it captured and remade her as the Queen of Blades. (StarCraft; StarCraft (manual))

Psionics and the zerg#

For the zerg, psionics was the ordinary medium of communication: members of the Swarm communicated largely through psionics, with only the higher command strains able to process and understand vocal commands. The zerg could sense psychic power and, being acutely sensitive to it, often sought it out, sometimes responding to it so strongly that they rendered themselves temporarily beyond the control of a leader; this sensitivity reached further than that of the terran wranglers. The amount of psionic control exerted over a zerg force shaped its intelligence, and without that control the zerg became little more than animals, the feral zerg who attacked everything on sight. (StarCraft (manual); StarCraft: Evolution; StarCraft: Brood War)

The Overmind, the cerebrates, and later Sarah Kerrigan and her broodmothers held the Swarm together through this psionic command. The United Earth Directorate turned the principle into a weapon during the Brood War, deploying a psi disrupter to fragment the zerg arrayed against it. After the End War the evolution master Abathur bred the chitha, psionic zerg whose strong presence could disrupt communication and command nearby zerg, demonstrating once again that for the Swarm, psionics was both the source of its unity and the means of its undoing. (StarCraft; StarCraft: Brood War; StarCraft II: Heart of the Swarm; StarCraft: Evolution)