The dark templar refused to submerge themselves in the communal protoss mind link, the Khala, preferring instead to strive as individuals. Zeratul holds the rank of prelate and is probably best known for his role in ensuring the survival of the protoss since the zerg threat first became apparent.
“I have journeyed through the darkness between the most distant stars. I have beheld the births of negative-suns and borne witness to the entropy of entire realities….”
It was Zeratul who overcame the prejudices of Executor Tassadar when they met on Char, and thus began to heal the rift between the Aiur protoss and the dark templar. It was Zeratul who was the first to slay a zerg cerebrate although the cerebrates had been thought immortal. Most of all it was Zeratul who returned to Aiur with Tassadar and set into motion the events that would rejoin the sundered halves of the protoss race and overthrow the oppressive rulership of the Conclave.
Zeratul went on to fight alongside Tassadar to bring about the destruction of the zerg Overmind during the invasion of Aiur, and then helped the protoss evacuate the planet as it continued to be overrun by the zerg. When the Swarm followed the refugees to the dark templar world of Shakuras, Zeratul helped recover the Khalis and Uraj crystals, which allowed the protoss to activate the xel’naga temple there and wipe out the invaders. Later, when the dark archon Ulrezaj threatened to destroy the Aiur protoss “violating” Shakuras, Zeratul was instrumental in thwarting Ulrezaj’s schemes.
But Zeratul also carries many terrible burdens. In the act of slaying the cerebrate Zasz, Zeratul became temporarily linked with the Overmind. Zeratul came to know much about the Overmind’s plans, but the zerg leader gleaned the location of Aiur itself from Zeratul’s mind, and so the seeds of the planet’s devastation were sown. Furthermore, Zeratul has a long and bitter history with the Queen of Blades, having been manipulated and betrayed by her more than once as she destroyed the remaining zerg cerebrates in order to secure her control over the Swarm after the Overmind’s death.
As part of her schemes, the Queen of Blades took control of the beloved protoss matriarch Raszagal. Zeratul later rescued the matriarch, but he found her to be irrevocably corrupted. Sorrowfully he took the matriarch’s life to spare her from continuing as the plaything of the Queen of Blades. With her mind freed by the deathblow, Raszagal thanked him and named him as leader of the dark templar. Such an honor Zeratul felt unfit to take, his soul too scarred by his experiences.
Well spoken, Concubine of the Zerg. But though we strike at you from the shadows, do not think that we lack the courage to stand in the light.
For the moment he focused on a more immediate concern: contacting any other nearby protoss who had survived the Queen of Blades’ treachery. Tracking protoss power signatures to an obscure moon, he hoped to reunite with his comrades and return to Shakuras with them in order to plan for the future. Instead of comrades, however, he found a former agent of the Queen of Blades – the enigmatic Samir Duran – engaged in breeding protoss/zerg hybrid creatures. Although Zeratul destroyed the facility, Duran claimed that it was merely one of many. Duran also revealed that he had been known by many names over the millennia and that he was not serving the Queen of Blades, but rather a “far greater power.” Deeply troubled by what he had seen, Zeratul went into self-imposed exile with only a handful of followers at his side.
Zeratul continued his search for answers, until he and Kerrigan were both lead to Ulaan–a moon once inhabited by the Xel’naga. After a skirmish with the Queen of Blades and her zerg minions, he uncovered fragments detailing a prophecy foretelling Kerrigan’s role as leader of the Swarm, and the coming of Amon, the fallen Xel’naga.
"James Raynor... I bring tidings of doom. I have pierced the veil of the future and beheld only... oblivion. Yet one spark of hope remains. You will hold her life in your hands... And though justice demands that she die for her crimes, only she can save us."
After deciphering the prophecy, Zeratul warned Raynor—through a series of visions—that without Kerrigan, Amon’s strength would be further bolstered by the zerg. He then confronted Kerrigan aboard her Leviathan, and told her she would need to claim the power of Zerus and the primal zerg in order to challenge Amon.
Zeratul now faces the judgement of his own people for having aided the Queen of Blades, and hopes his faith in the xel’naga prophecy will deliver the galaxy from destruction.