It was the second Era, or what would be later referred to as the Era of Fertility. Around this time, the gods who had worked hard to create and manage the Earth began to get overwhelmed with the amount of work they had to do, but then an astonishing discovery was made. When two god's conceived a child, it would also be a god (albeit a minor god, but still a god nonetheless).
This resulted in a large increase in relationships between gods and goddesses in an attempt to get helpers for themselves. One such couple was that of Ren and Mave. Mave had a large role in developing the earth, but it wasn't getting too difficult for her. Mave the goddess of humanity only had to create more humans, and it was the other god's who had to manage their behavior.
Perhaps out of pity, Mave decided to help out one of the god's with the highest degrees of workplace stress, Ren. Ren was the god of sin, during the early days of the earth his job was pretty easy as he would make the occasional person in each tribe create a sin. It was usually nothing major, but even when it was it wasn't too hard on him.
This easy environment unfortunately didn't last too long for him. As human's started developing into societies, their potential for sinning grew exponentially. It was incredibly hard for him to keep up. Mave saw this and proposed that they he have children for his work while Ren was on his way back to his home.
"Hey Ren, you look worse then ever."
"Oh shut up Mave. I used to have it so easy, but now look at me. I haven't had any rest in the last century."
"Why don't you just have children, everyone is having them now and I heard it makes work a lot easier."
"I would love to, but I don't have the time to ask anyone, this is the first conversation I have had in 5 years."
"Whatever, why don't we just have children then."
"Really?"
"Yeah."
"Thank you so much, my work is going to get a whole lot easier then."
Unfortunately for Ren, he didn't realize that his children would be the personification of a sin. This would make his plans for trouble free days, even less likely. Once Ren took Mave back to his place, they started the conception process.
Conception for god's was much easier than humans. All it required was a contract signed by each party, and then children would spawn in between the two who agreed. It was randomized whether the children would take after the mother or the father, but fortunately like Ren needed his children would come out with similar abilities to him. Once the contract was signed, eight babies spawned one after another from out of the ground in between Ren and Mave. They were octuplets.