The woman on the mountain - Tonra - might be Neporo. She was immortal, had power over dreams consistent with the descendents of Neporo, isolated herself because she thought she deserved it (Kalyba implied that Neporo comitted some great crime) and she had the jewel.
Samantha Shannon did say that Neporo ‘might’ have outlived Kalyba, but Tonra was dead when Dumai came to her.
Or was she? In her own writing, Tonra states that falling from a height and being dashed to pieces might not be enough to kill her. On the mountain, she might simply have slipped into a coma, and seemed dead when her body was found. Dumai, Nikeya, and Kanifa were all suffering altitude sickness when they found Tonra’s body - they weren’t thinking straight, and might have not checked for her pulse and breathing very well.
Also, Canthe/Kalyba had no pulse when it was checked. It might be that it was an illusion, but it might also be that the first to eat the fruit of the siden trees get their whole body paused - not just an end to aging, but no pulse either.
If Tonra is Neporo, then her hair still grew, but it might just mean that bodily processes slow to the point of being nearly undetectable. If Neporo, Cleolind, and Kalyba’s hearts only beat once a minute, it would be easy to miss.
This would also explain why Cleolind’s body in the tomb hasn’t decayed. Cleolind isn’t dead either - just in a deep sleep. With no pulse, she’d seem dead to anyone who examined her.
