The colossal gates of Sanctuary Zero continued to swing open slowly.
Their smooth grinding sound rippled across the surface of the black tower.
The air that poured out was far colder and cleaner than anything outside.
The underground city had been updating itself endlessly for centuries.
Not a single speck of dust stirred in the air.
No trace of moss or damage marred the door's edge, nor the long corridor walls visible from outside.
Every surface gleamed spotless, and the crystal lamps in the ceiling burned with steady light.
Even the faint hum of machinery kept perfect rhythm exactly as it had when the place first opened five hundred years ago.
The deep, clear voice of the ancient AI echoed again, closer and more alive this time.
"Zero Protocol activated. All temporary access restrictions lifted for registered entities."
As they stood transfixed, heavy, staggering footsteps sounded from behind the group.
Guardian Omega had finally arrived.
