It an organism from the deep that feeds off the pale heart

I feel like the Veil is some sort of paracausal artifact that helped Neomuna achieve this uploaded consciousness ordeal. Kind of like Mara achieving her own Throne World. That’s if I’m remembering the lore correctly. Haven’t really sat down to read it again… I like your explanation. My theory is that the Traveler isn’t dead, the people of the Tower are just assuming the worst. The Traveler has some sort of realm in it, maybe leading back to this metaphorical place where the Gardener and the Winnower slapped each other. The reason we can’t feel the light is because whatever entity is inside the Traveler has shut itself off until it makes a move to ensure its (or ours) survival. Hiding until we get there maybe? It’s definitely weird how no one was really freaking out about it. Just calmly “hey we ain’t dead tho :)” Or it is dead and it’s just a floating ball there now. Then we probably have to destroy whatever follows. Classic destiny style.

Paracausal power is a law of the cosmos. The Gardner made it so that it can’t be tampered with. Power will always exist, in some form or another. Gaining power from killing is a function of the Sword Logic. The Winnower embodies this function and it became part of cosmic law. I would say the two sides mess with the river. The Light by bringing us back from the dead, the Dark by keeping those who die from final death and able to return. Both sides. The Veil acted like a portal. The power of the Light comes from the Traveler. Yet the Witness didn’t just go inside. I’d say this leans towards the old lore about a hidden throneworld inside the Traveler.