Gar Anstak was a Mairan Jedi Master of the Old Republic who worked underneath Jedi Master Odan-Urr, the Keeper of Antiquities, at the Great Jedi Library on Ossus. From an aquatic planet near the Hapes Cluster, Master Anstak resembled a typical native of the planet Maires. He possessed black, rubbery skin and over forty tentacles which came in handy during his service as an archivist on Ossus. His own people, the Mairan, considered Master Anstak an outcast due to his Force abilities and the propensity of citizens of the Hapes Cluster to dislike outsiders and especially Jedi.

Coming from a watery world, Gar Anstak specialized in artifacts from water dominated worlds that were home to aqueous civilizations. The Jedi Master's collection boasted pieces from worlds such as Iskalon, Issor, and Drexel. Due to the necessity that Mairan require their skin to be constantly mosit and because the artifacts were water-based, Master Anstak established his offices in the submerged caverns of Imhar Canyon on Ossus annexed to the library.

When the supernova from the Cron Cluster, courtesy of Alema Keto of the Krath, destroyed the surface of the planet, Master Anstak's remote office location protected it from annihilation. However, landslides resulting from the explosion trapped Gar Anstak in his offices and hid them from the galaxy for millennia. Gar Anstak never managed to escape and his archives became his tomb. Before he died, Master Anstak created a holorecording for whoever might find him.