Born in 2224, he was the first son of Ambassador Sarek and the Vulcan princess T'Rea, Sybok would later become the half-brother of Spock. His birth came as a result of the only mating between his parents and his existence was kept secret from his father Sarek. Shortly after this event, his mother divorced his father and ascended to the position of High Master of Gol; a position which meant that she was perfectly within her right to annul the marriage. (TOS novel: Sarek)
Sybok was only three seasons old when his mother received illumination and took the position of High Master. His name was an archaic word which meant "seer" or "prophet" which was because his mother believed that he would become the salvation of his people.
From a young age, his mother taught him that emotions need not be suppressed but rather should be embraced which meant that he did not believe in the logical teachings of Surak-though he did hide this fact from other Vulcans. The young Sybok was given the name Shiav, which was an ancient word from the Vulcan language long dead religion which, when translated, meant "messiah" as she believed he would unite all religions by finding "The Source" known as Sha Ka Ree. As a child, his mother often told him the legend of Sha Ka Ree which she had devoted her life to uncovering and had written an academic paper on. This single-minded focus on finding the Source consumed Sybok, who promised his mother that he would take her to Sha Ka Ree. Despite all the teachings of Sha Ka Ree, his mother did not reveal the location of this mythical paradise and kept this knowledge to herself which she had learnt from her time amongst the Ancients; the katras that were kept within the Hall of Ancient Thought.
The teachings of his mother were considered heresy which eventually led to her stepping down from the position of High Master. This act meant that she was the least known of the High Masters of Gol; rather than be banished, she remained within the order though she was kept silent due to her beliefs. Eventually, she died and her katra was forcibly removed and placed within a vre'katra where it was interned within the Hall of Ancient Thought. Sybok believed that the actions of the Adepts of Gol contributed to her death and was kept from her, thus not allowing him to full his promise to her about journeying to the Source. He was even kept from the Hall during the time of the transference. After her death, he began living at the home of his father Sarek and his wife Amanda Grayson where he met his half brother Spock. In time, the attitude of the Kolinahru relaxed after his parentage was discovered after his mother's death. Sybok later attended the first anniversary of her death and the entombment of her undying spirit in the Hall of Ancient Thought. Once there, he was within the family's gardens where he began to cry as part of his embracing of emotions where this act was discovered by a shocked Spock. It was then and there where Sybok revealed to his younger brother that he believed Surak's teachings were wrong and that his younger brother should challenge the teaching of their elders. At this point, he was noted as being a powerful adept of the telepathic arts with knowledge of forbidden techniques that allowed him to, in effect, brainwash others (though Sybok believed that he was curing others of their pain). As a young man, Sybok was exceptionally gifted and possessed great intelligence. Many on Vulcan assumed that one day Sybok would take his place among the great scholars of that world. Sybok instead decided to become a revolutionary, and sought knowledge and experience forbidden by Vulcan beliefs. Rejecting the idea of pure logic, Sybok instead preferred to balance logic with emotion, and embrace what Spock would later term the animal passions of their ancestors.
During his studies, Sybok received visions given to him by what he believed to be "God", beginning his journey for a place in Vulcan mythology known as Sha Ka Ree. When he was barely an adult by legal standards, he was determined in the course of action set in finding Sha Ka Ree; Sybok used the anger he had felt over his and his mother's treatment to fuel his actions which he felt no regret in committing... Serving as a Watcher alongside Storel in their ceremonial role of guarding the Hall of Ancient Thought, Sybok violated the mind of the elderly Storel leaving him damaged in order to learn the layout of the Hall. Entering the vast maze, he journeyed into the central chamber in order to find the vre'katra of his mother T'Rea. Finding the receptacle, he mind melded with it, despite the risk of succumbing to madness. There he learnt of the rumored location of Sha Ka Ree within the Great Barrier. He planned to place the mind of his mother within his own in order to carry it to the Source. However, he was confronted by High Master T'Sai along with three attendants whereupon he lost contact with the mind of T'Rea. Angry, he believed T'Sai had silenced his mother only to learn from the High Master that T'Rea had willingly accepted true death rather than be interned within the Hall once again. His actions were considered a most heinous crime in this society, which led to him being declared Ktorr Skann; an outcast from his people who was exiled from the Mother World. (TOS movie, novelization & comic adaptation: Star Trek V: The Final Frontier)
By 2255, Spock had not seen Sybok in over a decade, and wondered from time to time if his half-brother was even still alive. Spock related this to the young Cyprian Merata in attempt to help her understand how he would likely respond if he crossed paths with his half-brother again. It was the first time in a number of years that he had spoken of Sybok out loud. (TOS novel: Child of Two Worlds)
In 2287, Sybok came to Nimbus III. Using an ancient Vulcan technique where he forced others to confront their deepest pains and draw strength from it, Sybok gathered a group of loyal followers, which he called the Galactic Army of Light. Sybok's forces then stormed Paradise City, which they easily captured.
Sybok then forced the three representatives of the city - the Romulan Caithlin Dar, the Klingon General Korrd, and the Human St. John Talbot to face their deepest pain. He then had Dar proceed to send a transmission out stating that they had been kidnapped and Sybok's group had taken over the planet. As Sybok hoped, this drew the attention of the Federation, who sent the USS Enterprise-A to the planet. Captain Kirk and his crew initiated a rescue attempt, which failed when the representatives all pulled their (forbidden) weapons on Kirk. Sybok and a small number of his followers were taken on board the Enterprise, and hijacked the vessel. Sybok took the Enterprise to the location where his visions lead him, beyond the Great Barrier. (TOS movie: Star Trek V: The Final Frontier)
Upon landing on Sha Ka Ree, it was revealed that Sybok was led astray by The One, which instead of a God was actually a malevolent entity imprisoned on the planet, seeking a starship to gain its freedom. Realizing what he had done, Sybok attempted to save the crew of the Enterprise by sacrificing himself at the altar of his "god." (TOS novelization: Star Trek V: The Final Frontier; TNG novel: Q-Strike)
After Sybok's death the controlling effects of the mind melds with the individuals Sybok had telepathic contact with wore off. However, the individuals Sybok had forced to face their pain still benefited from their experience. For example, the experience finally allowed Leonard McCoy to finally put his grief over his father's passing behind him. (TOS novelization: Star Trek V: The Final Frontier)
In an alternate timeline in which the Borg Collective invaded the Alpha Quadrant during the 23rd century, Sybok was one of those who died along with his crew in the relentless Borg onslaught of 2243. (TOS novel: Engines of Destiny)
In another alternate timeline created by Devidian interference throughout history after their defeat at the hands of the crew of the USS Enterprise-D, Sybok was a famous ambassador by the 2360s and who helped the Enterprise crew defeat Sela's attempt to conquer Vulcan. (TOS comic: "Split Infinities")
In another alternate timeline in which John Frederick Paxton destroyed Starfleet Command and ended the talks for the Coalition of Planets in 2155, Sybok was the only child of Sarek. His mother T'Rea died when he was a child. Given his revolutionary beliefs, he was banished from Vulcan in 2244 when he was 20 years old. By 2264, his father had not seen him in two decades and had no idea where he was. (TOS - Myriad Universes novel: A Less Perfect Union)
In another alternate timeline in which Surak died young and the Vulcans (or "Minsharans" as they were called) were little more than brutal savages, Sybok was a fanatical soldier in service to the warrior T'Pau. This version of Sybok possessed much of the same mental powers as his mainstream counterpart, and often goaded his enemies to "embrace their pain." (ST - Myriad Universes novel: The Tears of Eridanus)