On the note of the lesson we received from Minfillia & Co.:

We learned about how Primals differ from "souls" of men and those of ascians. We know that Primals have an "essence" that is in the Lifestream, which needs an aetheric boost to create a corporeal form in the physical plane. From the way Ramuh spoke, it seems he has been around in the Lifestream and world for a long time - particularly with his comments about darkness not being there in the beginning (were the Primals the ones alive in the 1st Astral Era? Who knows...). We got a lot of answers about the different planes, but we have yet to get one for "what is an essence" which has been a big part of the many primal discussion threads on these very forums.

I feel that perhaps Shiva might let us explore this idea of an "essence" in some way, maybe. Perhaps the "creation" of a primal rather than just a pure summoning?

Then again, I also thought she had tempered the Ishgardians! Who knows!