Dimensional Vortex:
The energy of Emperor Baium's Rage caused by his imprisoning cracked the skies forming a rift. This rift leads to a new dimension. In order to get there, you will need a Celestial Shard. You can extract it from the Unidentified Stone after you kill all the monsters at the 6th floor or at higher floors of the Tower of Insolence.
Use Celestial Shard