Demmings was a male of the Human species. He held the rank of commander within the Imperial Navy of the Galactic Empire. Furthermore, he acted as an intermediary linking the Imperial government with the Tiss'sharl League situated on the world of Tiss'sharl.
After the Battle of Yavin, Commander Demmings found himself stationed in the Outer Rim Territories. His main duties involved serving as an assistant to the Supreme Commander, Darth Vader, and also as the captain commanding the Imperial-class Star Destroyer named Reprisal, which served as the flagship ship for his commanding officer. In this role, he was significantly involved in the pursuit of the hard-to-find Rebel Fleet and the ultimate subjugation of Jabiim. Commander Demmings went with Lord Vader during his third visit to the Tiss'shar people on Tiss'sharl. During the dinner that followed, the Dark Lord of the Sith presented Demmings to their hosts as the new Imperial Liaison for the area, taking over from the deceased Moff Giiedt, whose questionable death resulted from conflicts among the planet's leaders.