None saw it coming. Not the Mortals. Not the Gods. Definitely not the Halbloods.
In the year 2030, the Old Gods woke up. This came as a big shock, as even the Gods had Forgotten they existed. A Race of Beings so old, they vanished before the current Gods even came into existence. A terrifying new threat that the God's could not hope to face.
The initial attack was horrific. It shattered the veil. These giant behemoths descended from the heavens and rose from the depths of hell, revealing the Supernatural to unsuspecting mortals. The ultimate ambush. Entire countries decimated. New York reduced to ash. Humanity helpless to fight back. At least they would be if it weren't for Demi-Gods. Children to the New Gods. Children of the Norse, Shinto, Greek, Roman and more Pantheons.
With the help of the Demi-Gods, Humanity was able to set up a few cities. Though, as suddenly as the attacks had begun, they ended. Leaving what was left of humanity to rebuild. Though with the existence of the Supernatural known to all, the Demi-Gods were called to defend Humanity from the lingering dangers. Monsters from the various pantheons and several new monsters that liked to prey on helpless mortals.
Some agreed and joined the Militaries of the various surviving settlements, others started or joined Private companies, and others went completely freelance.
It has been two years since the Old Gods changed the face of the earth, but we are still rebuilding. Recovering. With the Demi-Gods leading the Charge.
Oddly enough, no one has heard of the New Gods since the Old Gods attacked, and it has several Demi-Gods concerned.