Ke-tarya was an ancient Vulcan martial art. It evolved from a more deadly form called ke-tarya-yatar (or ke-tar-yatar). Spock studied ke-tarya as a young man, and used this knowledge to defend himself against Vulcan dissident Sered when the two encountered each other on the planet Obsidian. However, it was Spock's familiarity with Human fighting techniques that ultimately enabled him to defeat his opponent. (TOS novel: Vulcan's Forge)