Tolaris was a Vulcan and a crew member aboard the Vahklas, a civilian transport ship encountered by Enterprise NX-01 in 2151. Tolaris and the rest of the crew were considered V'tosh ka'tur ("Vulcans without logic") by other Vulcans for exploring a balance between logic and emotions. Tolaris forged a bond with T'Pol, and suggested she attempt to re-connect with her emotions. He used an ancient Vulcan technique known as a "mind meld" to help her achieve this, but T'Pol was uncomfortable with it and asked him to stop, which made him angry. T'Pol was then forced to violently tear herself away, leaving both parties with mental trauma. From this encounter, T'Pol would contract Pa'nar Syndrome, a disease that is precipitated by mind-melding improperly.
When Enterprise captain Jonathan Archer confronted Tolaris the next day, he brushed it off, eventually losing control of his emotions and tossing Archer across the room. Archer then asked the Vulcans to leave his starship. (ENT: "Fusion")