First of all a lot of people have saying the place that Cayde 6 is a afterlife inside the Traveller however to get my tinfoil hat theory out of the way. I believe that it is actually the Winnower and Gardens garden. My reason is that the viel uses both the light and the darkness to open the portal, I don't think that darkness energy would be needed to get into the Traveller there is no reason to. The Witness wants to kill the Light, the Gardener is in the Garden not in the Traveller the only way to kill the Gardener is to kill it in the garden. As many people have said the veil somewhat resembles a mushroom, I don't think it's connected to egregor, but the veil is definitely connected to consciousness and it's not a coincidence that the one place were, strand a subclass powered by collective consciousness is found right next to it on neomuna. I think the portal created by the witness isn't a portal but something to turn you into a paracausal entity to that enter paracausal reality. Finally I think that the Winnower, Gardener, light and dark are created by consciousness and paracausal reality of the garden is inside the collective conscious and the veil is a gateway that allows to enter the collective conscious of the garden