The Syrrannites were a Vulcan group during the 22nd century that followed what they believed to be the true teachings of Surak, the father of Vulcan philosophy. Believing that Vulcan culture in their time had become corrupt and no longer followed Surak's original teachings, they stood in vocal but peaceful opposition to Vulcan's government.
Specifically, the Syrrannites objected to the militaristic attitude that the Vulcan High Command had adopted. They also believed that Vulcans had disregarded other basic tenets of Surak's teaching by engaging in frequent deception, distrust, and anger as embodied by the use of the Vulcan monastery at P'Jem for espionage. The withholding of the truth from allies such as Humans, even though the Syrrannites did not fully accept the presence of non-Vulcans on Vulcan, was considered another sign of the cultural failings of the time.
In 2154, Earth's embassy on Vulcan was bombed by unknown forces. The government identified the Syrannite group as the main suspects. In particular, T'Pau, one of the movement's leaders, was implicated by the government. Investigating the bombing, Enterprise NX-01 Captain Jonathan Archer and First Officer T'Pol encountered Arev (who was actually Syrran himself) in Vulcan's Forge. While seeking shelter from a sandfire storm, Arev/Syrran was killed by an electrical burst from the storm. The injury was fatal but, before he died, Syrran transferred Surak's katra to Archer. (ENT: "The Forge")
Guided by the katras of Syrran and Surak, Archer and T'Pol found the Syrrannites' main base at the T'Karath Sanctuary within Vulcan's Forge, where T'Pau attempted to transfer Surak's katra from Archer to herself, but Surak's katra resisted this. The Vulcan High Command then began to destroy the Syrranites' base at the Sanctuary, to cover up their involvement in the bombing of the embassy, and to completely vanquish the nettlesome Syrranites once and for all. Among those who would survive were Archer, T'Pol, and T'Pau, who, before the destruction of the T'Karath Sanctuary became complete, began to search its lower caves in order to find the long lost Kir'Shara, Surak's original sacred texts. (ENT: "Awakening")