The O-Gaub was the supercarrier used by the Val-Fasq agent Nefuria during her invasion of the Transbaal Empire constructed by Val-Fasq designs and manufactured by the recovered core of the Black Moon.
After its destruction by the Chrono Break Cannon during the final phases of Eonia's coup, the remains of the Black Moon secretly managed to escape to a remote star system. Once there, the Black Moon merged itself with a large asteroid and with its weapons production plant still intact, it began to regenerate. Previous officer of Eonia's troops Rezom soon rediscovered the new Black Moon and once again used it as their HQ.
The O-Gaub was created when the Val-Fasq agent named Nefuria secretly took control of the new Black Moon. Using information stolen from the Black Moon's core and combining it with Val-Fasq technology, she commanded the Black Moon's weapon production plant to construct the massive ship within the asteroid.
The O-Gaub was freed from its cocoon after the Elsior destroyed the new Black Moon with the Chrono Break Cannon. The Elsior's follow-up attack on the O-Gaub failed completely, but it managed to escape with Noa's aid before the O-Gaub's counterattack could destroy it. Afterwords, Nefuria set a course for Transbaal with the aims of conquering the Transbaal Empire and also acquiring the technologies of the White Moon. Along the way, she destroyed the Transbaal fleets in her path and captured several orbital mines to supply the O-Gaub's production facilities. The O-Gaub was eventually destroyed near Transbaal in Operation Angel Slap conducted by the Transbaal Armed Forces and spear-headed by the Elsior and the Angel Troupe. GA-007 was able to get close enough to disable the O-Gaub's shield with the Field Canceller, after which it was destroyed by a point-blank shot from the Chrono Break Cannon.
The O-Gaub was gigantic in size and capable of housing countless battleship sized vessels within it's vast hull. It also retained its Black Moon construction facilities, which it used to produce a massive Val-Fasq support fleet to surround itself and produce new escorts as needed. Even without escort, the O-Gaub was a formidable vessel with enough firepower to single-handedly obliterate a Transbaal defense fleet.
The O-Gaub made extensive use of the Negative Chrono Wave, adapted from the Black Moon. This is a wave form which interferes and cuts out the Chrono String Engines of nearby enemy ships, rendering them completely helpless. The Negative Chrono Wave was also modified using Val-Fasq technology to create a shield around the O-Gaub which nullified incoming weapons fire; this shield withstood a direct hit from the Chrono Break Cannon without incurring any damage.