Site 12-C, catalogued as a Deep Reliquary, sealed beneath a hillside and preserved almost intact, the finest example yet recovered of the Ancient practice we now call Anticipatory Interment.
The chamber was stocked as a tomb, but no body was ever placed inside it. This is the great puzzle. The Screen People filled these vaults with everything a soul required for the afterlife: towers of sealed metal cylinders containing preserved sustenance, vessels of purified water, luminous lamps that needed no flame, and a great bound codex, hand-marked, which we read as a book of survival prayers.
They laid in weapons, too, arranged with care, to ward the deceased against the demons of the next world. And then they left the vault open to no one and sealed themselves out.
We now believe the occupant of such a tomb was the living builder. Faced with prophecies of a coming Unmaking, a devout Ancient would descend into the earth alone, not to die, but to outlast the death of everything above. The wear patterns tell the rest: a single chair, deeply worn at one seat. A wall of tally-marks, counting days that did not end. Dust undisturbed on the sustenance cylinders, most never opened.
The Unmaking, of course, never came. The world above continued its ordinary hum, indifferent, while below the ground a faithful few kept watch over an apocalypse that forgot to arrive.
These were a people who could not bear to be surprised. So certain the sky would fall, they buried themselves alive to greet it, and mistook their own fear for foresight. We do not mourn them. We envy them a little.
They believed, with their whole hearts, that the end would be grand enough to require preparation.