DREAD's World (2/6): The prophecy of the "Dawn of the Vile Moon"

The Dawn of the Vile Moon

Gustave Doré—The fourth Horseman, Death on the Pale Horse (1865)

What players might know:

51 years after the Severance and the arrival of the Humans on Perfu, a mystical event rattled all civilisations in the world:
During that moonless night, all seers, augurs, diviners, oracles, and fortune-tellers had the same vision.
The "Dawn of a vile moon" was coming. Noone could tell when, but all, from the goblinoid shamans to the High-Harbingers of the forest-folks, agreed on the fact that it was coming.

"Whence the moonless night reaches her middle and the stars align, a gaunt rider will fly before a hitherto unknown bloody moon, followed by his legion of horned minions.
Shepherded by their bleak General riding a TerrorGeist, this dread-swarm will bring war to our lands and herald an age of chaos, destruction, and despair.
Brace yourself for darker times, folks of Perfu, for the Dawn of a vile moon is coming erelong"

Only Pythonia, the oldest human oracle, saw the "Dawn of a vile moon" for what it really is: The arrival of the Infinite Horde on Perfu.
She recognized the leader of the armies heralded by the "Dawn of a vile moon" as Phongor — the Inquisitor of Hell — who was the General of the Infinite Horde on the lost home of humanity.
In the years following what will be called the "Night of the Prophecy", the cultures that were in contact exchanged information and realised that all their seers had the exact same vision of the future, reinforcing the credibility of the Prophecy.
Since they already were perceived as bad seeds, the human kingdoms failed to inform their partners that they identified the threat coming towards Perfu.
Since then (around 200 years), an arms race has taken place, but since the Dawn of a vile moon did not happen, those weapons have been used against neighbours. Otherplace, cults attempting to hasten the coming of the Dawn of a vile moon have flourished and withered.
The coming of the Dawn of a vile moon is not forgotten, and times are getting darker.
Will your Characters be ready and survive the Dawn of a vile moon?

How did the devils come to Perfu?

It took them 666 moon cycles, but the devils that were mingling with humanity, possessing a host or assuming a covert identity in urbarin society, did find a way to reach through the planar boundaries, after traveling with humanity to Perfu during the Severance.
The bloody sacrifice executed to power the devilish spell nearly razed the two biggest goblinoids tribes around the inner sea. Even though scouts from different nations did find gruesome rests of the slaughter, all nonchalantly ignored the finding, considering it condescendingly as a random act of violence in a depraved monstrous "society".
Contact has been made to the Infinite Horde and since then, the devils have worked toward the opening of a bridge to allow passage to Perfu to the rest of the Infinite Horde