The Khal were a civilization on the planet Vulcan who flourished at an unspecified time on Vulcan where they resided at R'sev. This period was considered similar to the cultural awakening and developments of Sarpeidon's Lakreo Valley and Earth's Tigris-Euphrates civilization.

In 2270, Zar decided to return to Sarpeidon's distant past to live his life and used the Guardian of Forever to travel 5,000 years ago to the Lakreo Valley. (TOS - The Yesterday Saga novel: Yesterday's Son)