The ancient Vulcan philosopher who led his people from violence to logic, recreated in The Savage Curtain and seen in visions in Enterprise.
Surak is the most revered figure in Vulcan history, the philosopher who taught his people to master their violent emotions through logic, at a time when they were destroying themselves in war. His teachings led to the founding of modern Vulcan society and to the split with those who later became the Romulans.
In The Savage Curtain, the Excalbian Yarnek creates a version of Surak to fight beside Kirk, Spock and Abraham Lincoln. Surak goes to negotiate peace with the opposing side, staying true to his philosophy, and is captured and killed.
In Star Trek: Enterprise, Surak's katra, his living spirit, appears to Jonathan Archer and guides him to the Kir'Shara, the artifact containing Surak's true teachings, which helps reform Vulcan society. Surak was played by Barry Atwater in the original series and by Bruce Gray in Enterprise.