Ke-tarya-yatar was an ancient Vulcan martial art, considered one of the most difficult, as well as the most dangerous, to master. (TOS - Vulcan's Soul novel: Exiles).
Ke-tarya-yatar dated back to Vulcan prehistory, and was used only as a means of assassination, largely among the te-Vikram Brotherhood. With the development of tal-shaya as a quick and merciful method of execution, ke-tarya-yatar fell out of use, and evolved into a fighting and exercise regime known as ke-tarya.
By the 23rd century, only historians were familiar with ke-tarya-yatar (though by the name ke-tar-yatar). Vulcan dissident Sered was able to teach himself this ancient fighting method, and used it against Spock when the two encountered each other on the planet Obsidian. Spock was able to defeat him through his familiarity with ke-tarya, and with more Human fighting techniques. (TOS novel: Vulcan's Forge)
- It is an assumption that the same ancient martial discipline is being referred to in Vulcan's Forge and Exiles, though by slightly different names.