Shadow monarch in DXD (Male ocxcrossover)

I do not own Solo leveling, DXD or Tensura. They belong to their respective writers!
It is my first fanfic and English is not my first language, so I am sorry for any mistakes!
I am not a crazy fan of the DXD, even so I will try to follow the plot. Also, I will try to add some aspects of the world of Solo leveling into the DXD world.

Now to the description of the story.
Before the creation of humanity, there was the ultimate being which created fragments of light to make them fight with each other. However, the fragments of light killed their creator. However, the brightest fragment of light who was the only one to take the side of his creator was killed as well, but after his death he was given last gift from his creator. It was the ability to rule over shadows and death. He wanted to avenge his creator. However, after a very long time, he understood why his brothers and sisters had done that so he gave up and tried to find new meaning in his life. The fragments of light went to another universe while he was left to protect Earth. After a very long time, he has fallen in love with one woman who was a devil. She showed him so much love that they married and had a child in the underworld. He decided to stay there however this couldn't continue for long. She was betrayed by Lucifer and other Satans, because she didn't want to help them conquer the heaven and killed while Ashborn was away with his army and son to have fun. He was enraged and killed Lucifer and stayed in the very remote part of the underworld to raise his son. After his son became old enough, he did what the fragments of light asked him and used himself and his wife to become shields which will protect the world from outside forces and at the same time he could get eternal rest with his beloved which he wished for a very long time.