The Syrrannites were a Vulcan dissident group who followed the teachings of Surak closely during the 22nd century. Syrrannites believed that Vulcan culture at the time had become "corrupt" and no longer followed the original teachings of Surak.
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 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, the United Earth Embassy on Vulcan was bombed by forces unknown. The Syrannites were strongly suspected. 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 was killed by an electrical burst from the storm. The injury was fatal but, before he died, Arev transferred Surak's katra to Archer. (ENT: "The Forge")
Guided by Syrran and the katra of Surak, Archer and T'Pol discovered the Syrrannites' main base at the T'Karath Sanctuary, where T'Pau unsuccessfully attempted to remove Surak's katra from Archer. The base was subsequently destroyed by the Vulcan High Command to cover up their involvement in the bombing of the embassy. Among the few survivors were Archer, T'Pol, and T'Pau, who then began a search to locate the Kir'Shara. (ENT: "Awakening")