Over centuries of watching Man's tumultuous relationship with the Gods, the Angel Samael, one of YHWH's loyal servants, hatched the plan to eradicate the realm of man, and bring the Age of Gods back. To do so, he opened a tear into the sky, directly accessing the unknowable realm of Irkalla. Almost immediately, millions of Demons escaped through the breach, invading Earth. This would be the beginning of the period of strife known as the War In Heaven.