The end of the puzzle forms a ring, a lot like armillary pieces and unity portal itself

Seems multiversy to me

Barret did find an artifact of his own but for whatever reason he seems to be special just like the player. If you choose to skip the main story on NG the surviving members of Constellation can go find the artifacts for you, but none of them mention having visions when they return, and Barrett is still the only one who can get powers

I don't think the temples make us Starborn, but I do think they imbue us with some of the same power that Starborn are made of, and like the artifacts, the temples are a stepping stone to the Unity

Whoever controls the unity, temples, and artifacts seems to be intentional with who they give power to, and they leave breadcrumbs to find the unity starting with the first vision

But why are Barrett, the player, and the unnamed owner of Petrov's artifact special? Why are they chosen to have visions that lead them to the Unity and others are not?

That's what perplexes me 🤔

IIRC the temples don't actually require anything special to open

Barrett is able to get a power despite not having an artifact in his personal possession, and we interact with most of the temples when our armillary pieces are either aboard our ship, at the lodge, or at an outpost

Digging deeper, not everyone who pulls an artifact out of bedrock seems to have a vision, and that makes me think that the key to unlocking the potential of the temples is tied to something beyond material possession