Many empires were outright destroyed by the cataclysm, but not the Tua'Thuan. They lived in relative safety on their far flung islands while the world burned. As such, they didn't need to rebuild after the cataclysm, and instead had time for greater undertakings. The greatest of which was the Hub. The Tua'Thuan are fond of using planar travel, but even the Tua'Thuan aren't sure of the true nature of the hub, whether it is between planes, or just some odd plane where gravity is repulsive is unclear. What was clear to the Tua'Thuan was that their druid council's had grown corrupt.
One of these corrupt druids hired 4 adventurers to raid a warehouse within the hub to recover an important (but non-magical) artifact. It had been placed on a pedestal which proclaimed that the artifact would save all that is and ever will be. When the 4 went in to investigate they met with immediate resistance. But as the battle seemed to be coming to the close, one of the defenders of the artifact retreated through a planar gate to safety. The adventurers followed to a baren plane that seemed devoid of life. Further investigation suggested that this was just a hidding place to buy time to find a true hidding place within the hub.
The chase was on to catch Newcomb (the guard who retreated with the artifact). The party discovered that Newcomb was part of a secret society that wished to hide the artifact from corrupt druids, which the party then decided they had been employed by. The party went after Newcomb to the material plane, not to take the artifact, but to help defend it. But, as the party neared the portal to the material plane, the section of the hub with the portal gave way and began falling to oblivion, and to make matters worst, bounty hunters rained from the sky using boots of flight to secure the bounty on Newcomb. The party overcame however, and teamed up with Newcomb to escape to the Material Plane.
The party lead by Newcomb went to his occult society, which sent the party to hide the artifact (called by some a world tree). They went through a portal which transported them to the mainland of the continent on the material plane. But the portal transported the party into a building that was infested with a giant beast. The party killed the beast, but that caused the building to fall. It is unclear if anyone survived, but whatever happened, the world tree (an intrinsically untraceable artifact) will not be found without extensive efforts.