Byss was a planet of paradoxes. It was located both in the Outer Rim and the Deep Core. It was an arid planet inhabited by violent Abyssins, and it was an abandoned planet with lush fields and ancient ruins. This probably had something to do with the Rakata. The Republic discovered the planet in the Outer Rim, but did not understand the nature of it until much later. The Emperor had a personal retreat built there, and did some crazy experiments there for awhile, trying to figure out how it worked, but all he did was fill it with Dark Side energy. Eventually he got bored (and drunk) and took over the controls of the Star Destroyer Pedanticator, crashing it into the planet. The crew probably could have stopped it long before the impact, but they didn't for some reason. This somehow resolved the paradoxes and left the Galaxy with only on Byss. The crappy one in the Outer Rim, where the Abyssins lived.
Notlob and Myo were both Abyssins from the planet Byss. They hung out in the Cantina on Tatooine, but were never there at the same time. This was possibly because of their paradoxical nature, but they may have just had conflicting schedules.