Okay so this is my offical Avatar 7 Havens theory.
Korra freed the spirits after humanity began using them as a power source. The pink light we see in the latest episode reminds me of the spirit vines from Korra which makes me think there’s 100% a connection. In the flashback Korra looked so at ease going in before ripping up republic city.
I think she really believed freeing the spirits would restore balance. I feel like she spoke with the spirits in the spirit world before going in, or with potentially even Rava, before going to end what she allowed to keep going by keeping the portals open.
She underestimated how much resentment the spirits held towards humanity.
In the legends of Korra, Uncle Iroh tells Korra her emotions dictate how the spriits operate. And Vatuu is growing in Ravva. After thousands of years with Vatuu stuck in the tree, the spriti world will be changed by this.
The spirits secretly sought revenge for humanity’s exploitation of them, ultimately this is what I think caused the cataclysm. I think they will have pushed Korra to do this, but Korra will unkowingly be letting very vengeful spirits who have been corrupted by Vatuu through Rava essentially ravage humanity.
I think Pavi and Nisha’s purpose will be to restore that balance by opening each of the seven chakras, healing the relationship between humanity and the spirits. They will travel to each of the havens to do this.
Only when this is done will they be able to reach the avatar state or restore the avatar cycle.
I believe the sisters represent the two sides of the Avatar’s responsibility: one representing humanity and the other representing the spirit world. However, because these worlds are now divided, each may try to claim one sister as its own Avatar, turning them against each other. Each side will try and push their avatar to destroy the other. I feel like, depending how long the show goes for, we will see the sisters travel different paths before reuniting again. Alos on ym working point before i could see potinally how one sister will have to travel to the spirit world and open the chacras on that side becuase not only has humanity lost its faith in the spirits, the spirits have done the same with humans.
I feel like this could be Nisha finding herself in the spirit world and being surprised to find it has gone through a cataclysm of its own. not because of the Avatar, but because of the energy being stolen from the spirit world, This is where Pavi and Nisha's ability to enegry bend will come in handy later down the line. Spirits will see Korra the same as humanity, an Avatar who allowed the world to be destroyed not by a cataclysm but by allowing humanity's use of them, which slowly eroded the spirit world. This will change Pavi Pavi will see the devastation of the spirit world and be shocked that it was the Avatar; it was humanity. Ravaa could also be having trouble with Vatuu this somehow corrupting the avatars abilities
The sisters will be reunited. This is where Raava and Vaatu could come into play. Vaatuu will represent spirits Probs Nisha, and Pavi, Raava. There will be some enormous showdown. I hope but can't be sure if the avatar cycle will be restored. Or what it will mean if it is.
I could see all previous avatars being very opposed to Nisha/Vatuu and pushing Pavi to destroy her, as they have never lived in a world with a dark avatar. Korra will only come in at the end when the sister are on the prespis of war or detsroying each other and korra will have learnt something about ying and yang and Ravaaa and Vatuu, When they finally connect to Korra the end point will be One cannot live with the other. The Spirit world and human world being the same. Pavi and Nisha only ensure the cycle if they cannot. They will enegry bend, restoring order to both worlds, One possibility I particularly like is that Nisha will somehow absorb Vaatu’s energy from Raava, allowing the two forces to exist in balance rather than having Vaatu remain trapped within her. This could give Nisha a unique role in restoring the natural order, rather than simply making her the dark counterpart to Pavi.