Kat can only enter this area though Gade, a creator. When there, flowers will point to the area you need to go to next after defeating each set of nevi.
Like the other Rift areas there is a rare nevi located here. For details regarding it look here.
To find that Rare Nevi, turn around and you will see a massive pillar. On top of it, there is a Ghost Traveler, and, if you go to the bottom, you will see a hole (see the images). Enter it and you will find the rare Nevi. It is a small Nevi, and, like other Rare Nevi, it is green instead of red. Defeat it (recommnded by using Gravity Kick), and it will drop an enourmous ammount of purple gems, which you can use to unlock challenges and evolve Kat's abilities.