• The Witness was once an entire species
• They discovered the Traveler buried on their home planet.
• The Traveler uplifted their civilization and basically they got bored and needed purpose.
• This led them to seek out The Veil. They built the pyramid ships to search for the Veil.
• The Veil is the Darkness equivalent of the Traveler. Not the pyramid ships.
• The Witness saw the light as a chaotic force to be tamed and tried to use the darkness/Veil to tame it and create the final shape.
• Traveler said nope and began running.
• The Witness’ race mass suicided and used the Darkness to combine their consciousness into what we know as The Witness.
• All the crumbling statues around the pyramids are the remains of its species.

Some pretty dark stuff with the origins of the Witness. I don’t think it’s quite clear what the final shape is yet.