In 2268, his mission was to represent Tellarite interests at the Babel Conference. He opposed the Coridan admission into the Federation, due to Tellarite mining interests on that planet. He was an outspoken opponent of his Vulcan counterpart, Ambassador Sarek. At a cocktail party aboard the ship, Ambassador Gav quarreled openly with Sarek about the admission of Coridan into the Federation. He demanded to know how Sarek would vote. He confronted Sarek later, and again demanded to know how he would vote. When Sarek told him that he would vote for admission and alluded to illegal Tellarite mining operations, Gav physically confronted him but was knocked down by Sarek.
Gav was later killed by Thelev, an Orion spy posing as a member of the Andorian delegation. Gav's body was hidden in an engineering circuit bay located on Deck 11, Section A3. Thelev then used the tal-shaya, a Vulcan technique, to incriminate Ambassador Sarek. (TOS: "Journey to Babel")
The script for "Journey to Babel" gives a description of Gav's voice, calling it "rough, grating, and accented in some way... as though English is very alien on his tongue."
In what was an expensive design at the time, John Wheeler wore makeup that consisted primarily of a one-piece foam latex appliance that covered the central part of his face. The piece was glued on in such a way that the actor's eyes could hardly be seen, and, as a result, Wheeler could barely see where he was going. Subsequently, he had to tilt his head back when he was reading his lines, in order to see through his makeup appliance. It was this tilt that gave the impression of Gav's being aloof and superior, and it added immeasurably to Wheeler's performance, even though it was unintentional. In order to complete Gav's makeup, a beard and mustache were hand-laid to blend off into the rest of his hair. The mustache helped to conceal the edge of the snout and formed an interesting effect with the character's bushy eyebrows. Gav's look was topped off with character gloves. (Star Trek: Aliens & Artifacts, p. 49)
In the Star Trek: Myriad Universes novel A Less Perfect Union, in one alternate timeline, Gav was the Tellarite representative to the Interstellar Coalition, and represented Tellar when United Earth petitioned for membership into that body.