4,000 years before the story of Percy Jackson began the Gods, Hades, Chiron, the Fates, and the Oracle sat together. During the usual meeting, on the Winter Solstice, the Oracle, Chiron, and the Fates barge in.
The Oracle has foretold a prophecy that can change or destroy the world, a prophecy not even the Fates have a say in. They exchanged looks and swore, on the River Styx, to never tell anyone of this until the prophecy begins.
One has been found
The other is hidden, safe and sound
When their eyes first meet
The heart of the storm will began to beat
Sons and daughters of the gods
Will battle against all odds
Magical beings brought to the light
Sent forward to fight
As the seek for the thing most sought
Gods are being caught
The dead brought back.
Thus begins the attack
For she is the brightness
That will light up the abyss
Author's Note: I don't own Sisters Grimm or Percy Jackson characters, but the rest is mine.