The tunnel leads to an underground city…
The city is full of silhouette people. They don’t seem to notice us. Shiloh sees in a vision grey cracked skin and no rib cage, some with organs just on display. It’s how they were. They walk on all 4s. They flock to the source of light in the cave city. A wind comes from the light, and a deep breath comes from it (loud). All of these people, the entire city, are shadows according to the mask. They have regular city amenities (park, water, etc.) They did not invent writing. Notably, the beacon wipes out ‘all traces of civilization except the buildings themselves.’ ‘As if they vanished all at once.’ Breath in the vision might signal a turn of the ages?
Every stained glass window on the huge building depicts a bird in various forms of flight (diving, flapping, etc). Statue of bird is what the light shines upon. It is standing with wings spread upwards (eagle, falcon style bird). Every shrine to the bird except the main one is defaced. Reading the runes is impossible as they were scratched out. Charred books? When the light hits the shadow people they turn into golden glowing majestic people. They are still shadows, but inverted. On the ethereal plane, the light is less radiant and more shadowy and pale. The main religious statue has beautiful crystals that reflect light in the wings.

An exchange between the people of Bral and the party

You are shadow and light. We are balance. Who are you? No remember. Teach us through scripture.
When you fell we found you. The great war. You do not remember?
The War of Dawn and Dusk?
We do not know that name. Are you alive?
What is your name and what is mine?
I am Ukkoto. You are the Luminos.
Numinos?
Luminos. Have you come back?
Alive. Fallen. Lost. Don’t remember. Where did I fall?
Here. Are you hurt?
I don’t know. What is the light?
It is you?
Have you been there?
//They begin to argue and kill one another//
Stop.
No more.
I am not the Luminos. We are balance. Alive. Lost. A war against darkness.