The captain of a ship of Vulcans who have rejected strict logic to explore their emotions.
Tavin commands the Vahklas, a Vulcan vessel crewed by V'tosh ka'tur, Vulcans who seek a balance of reason and emotion. In Fusion he hails Enterprise near the Arachnid Nebula when his ship needs repairs, explaining that his crew left Vulcan eight years earlier to explore themselves rather than the galaxy.
His ship's sensors help speed up Enterprise's survey of the nebula while the repairs are made. The visit turns sour after his first officer Tolaris forces a mind meld on T'Pol, and Archer orders the Vulcans to leave.