The Kir'Shara is an ancient Vulcan artifact containing the original writings of Surak, recovered by Jonathan Archer in 2154 and used to reform Vulcan society.
For centuries the Kir'Shara was thought to be lost. In 2154 Archer, carrying the katra of the Syrranite leader Syrran, crossed the Forge desert with T'Pol and found it hidden in an ancient sanctuary.
The artifact proved that the Vulcan High Command had strayed from Surak's teachings, and it exposed the High Command's cooperation with Romulan agents. Its revelation brought down the High Command and began a reformation that led Vulcan into a closer partnership with Earth.