Sybok was the firstborn son of the Vulcan diplomat Sarek and a Vulcan princess, and was half-brother to Starfleet officer Spock. A revolutionary, Sybok sought experience and knowledge which were forbidden by Vulcan belief.
Early life
As a young student, Sybok was considered to be exceptionally gifted, possessing great intelligence, and it was assumed that he would one day take his place amongst the great scholars of Vulcan. However, Sybok rejected his logical upbringing and chose to embrace emotion, believing that the key to self-knowledge was emotion, not logic. When Sybok encouraged others to follow him, he was banished, never to return.
Quest
During his studies, Sybok received visions given to him by an entity whom he believed to be God himself, and began a journey for a place in Vulcan mythology known as "Sha Ka Ree," from where all of existence was said to have originated. In 2287, Sybok's visions lead him to Nimbus III, where he gathered a group of loyal followers, known as the Galactic Army of Light. By using a telepathic ability to seemingly release an individual's deepest-held psychic pain, he was able to manipulate others in to joining his cause. With his growing band of loyal followers, Sybok was easily able to capture Paradise City.
Sybok confronts "God"
In an effort to gain access to a starship, Sybok subsequently kidnapped three ambassadors to Nimbus III; St. John Talbot of the Federation; General Korrd of the Klingon Empire, and Caithlin Dar of the Romulan Star Empire, and successfully manipulated them into joining him. This eventually led to a failed rescue attempt by the crew of the USS Enterprise NCC-1701-A, wherein Sybok was reunited with his brother, Spock. Commandeering the Enterprise, Sybok had the crew set a course for the center of the galaxy, where he believed Sha Ka Ree existed, beyond the Great Barrier. Although Captain Kirk insisted that the Enterprise would be destroyed attempting to penetrate the Barrier, Sybok was eventually vindicated when the ship was able to do so without incident, and discovered a planet on the other side. Traveling to the surface with Kirk, Spock, and Doctor Leonard McCoy, Sybok was eventually confronted with the fact that the being which had given him his visions was not, in fact, God, but rather a malevolent alien entity who had been imprisoned within the Great Barrier, and who had manipulated Sybok into providing him with a starship with which he might escape. Realizing that he had made a terrible mistake, Sybok confronted this being, sacrificing his own life to save the crew of the Enterprise. (Star Trek V: The Final Frontier)
Appendices
Background
The role of Sybok was written for popular actor Sean Connery; however, this did not come to be and the role was, ultimately, played by Laurence Luckinbill (Star Trek Encyclopedia). According to the Star Trek Chronology, Sybok was born in 2224, based on conjecture that Spock was born in 2230. Sybok's back story has been considered apocryphal by some sources, including Gene Roddenberry. It was stated in TNG: "Sarek" that Sarek's first wife was from Earth. Clearly, this was intended to be a reference to Amanda and that Sarek was not married to a Vulcan princess. Admittedly, Star Trek V never explicitly says that Sarek ever married the princess, nor was it stated in "Sarek" that Amanda was Sarek's first Human wife, or how many previous wives he had, only that the Vulcan princess was Sybok's mother. It seems likely that Sybok would identify himself with the V'tosh ka'tur movement, but as that concept was invented for Star Trek: Enterprise, the exact phrase was not used onscreen.