Metal Throne was Fat Ball’s personal domain in the Nine Serenites, and can be called as the Nine Serenities within the Nine Serenities. The domain was heavily fortified so that other Nine Serenities Rulers can’t breach its defences easily.
Fat Ball trapped Song Shuhang inside the Throne in order to prevent White Two from rescuing Shuhang when he was being interrogated. Song Shuhang managed to escape by using the aura of imperishable, luring a Great Turtle of Disaster into swallowing him. From the turtle’s stomach, Shuhang entered his Core World.
Undeterred,Fat Ball used 《Time Reversal》 to drag Shuhang back into the Throne. At that time, the Core World entrance was opened to let White enter, which allowed Shuhang to be dragged back, with White in hot pursuit.
Meanwhile, White Two detected Shuhang’s aura in the Nine Serenities and came to investigate. He then found the Metal Throne without its owner. White Two promptly took the chance to move the entire domain into his Evil Lotus World.