((This is an alternate timeline plawt where the Old Ones were not put down in time. Now there's doom. Events here have no impact on other [Nexus] threads.))
That Day would be easy to know, for then mankind would have become as the Great Old Ones; free and wild and beyond good and evil, with laws and morals thrown aside and all men shouting and killing and revelling in joy. Then the liberated Old Ones would teach them new ways to shout and kill and revel and enjoy themselves, and all the earth would flame with a holocaust of ecstasy and freedom.
The blasphemous pillars of Rl'yeh rise from the foam, sea water pouring from the sunken city as it rises once more.
The waves roar and thrash against the ancient mausoleums and sepulchres of Rl'yah, as though trying in vain to beat it back into the depths once again.
The tombs open, horrors long since forgotten by all but the most irredeemable of mad-men flooding from those noisome pits as a great wave of insanity.
Cultists whirl and reel and worship at a great door. A door that even now begins to ease open with a bone-grinding sound of stone on stone.
A thing like a mountain of green foam and rises from that yawning chasm, crushing the cowering cultists under foot as a man might tred on ants whilst taking a morning stroll. Formless and yet formed, terrible to behold, clawing at the mind with mental tendrils of terror and madness.
With a single impossible stride the thing low looms over the fallen form of K'rax-Naggath, reaching down to seize one of the Old One's claws in its own.
The hand of the Warden of the Veil is driven into space itself, burning sigils etching themselves across heaven and earth. With a horrific wrenching twist the doors are thrown open. And all at once living nightmares descend upon what was once the world of mortals.