Masc was a male Denobulan Starfleet officer in the 24th century. In 2359, Masc served together with Counselor Deanna Troi, and at that time also knew her mother, Lwaxana.

By 2374, Masc held the rank of Admiral, and was in command of the Tenth Fleet, assigned to defend the planet Betazed. Masc was running a training exercise when the Dominion attacked and occupied Betazed. Admiral Masc was forced to order the Tenth Fleet to retreat, and to notify Starfleet Command that the planet had fallen. (ST - Tales of the Dominion War short story: "The Ceremony of Innocence is Drowned")

Admiral Masc informed the crew of the USS Enterprise about the fall of Betazed soon after. (ST novel: A Time for War, A Time for Peace)

By 2381, Masc was in charge of the Luna-class exploration program and ordered Captain Riker to continue with the USS Titan's mission of exploration despite the Federation's situation after the Borg attack. (TTN novel: Over a Torrent Sea)