They controlled the affairs of earth, with life being the reason behind existence, and death being the havester of souls after life has withdrawn its essence from a mortal. Rebirth however is nothing but a choice maker, she chooses who life is and gives its essence and whose soul can be harvested in other words, she chooses who dies or lives.
But then, there was the fall of demons, supernatural beings were cast out of the great realm to earth and their presence caused a lot of chaos.
They mingled among humans and their divine abilities made it harder for death, birth, and Rebirth to take care of the mortal.
The demons killed whoever they wanted to, and Rebirth had no power against it since the demons were more powerful than she was.
Death had a hard time harvesting souls, as much as he could because leaving them wandering would distort the balance of existence. So there was only one solution.
