DEADLYSHADOW
Seriously, that's all about history, I'm disappointed author, there wasn't even a construction and resolution of the mc's character, we didn't even see a fight against his enemies, you just made a description that he conquered all the domains of death and destruction. With all 11 chapters the only one that had a character growth of the mc was when he was reborn as a shadow monarch
Honestly, if you do make a multiverse, I hope it will be in the form of traveling to other worlds through the system or the dimensional gap, and not directly adding other worlds into the dxd universe. Whenever several universes are combined into one, everything loses logic and meaning. I was never a big fan of crossover universes into one as they have different power sources and world history and everything loses meaning and logic when merged. The only universes that I don't mind seeing included in crossovers set in the current era like dxd, would be animes without powers or something special. Like komi San, kaguya Sama, Prison school, kakegurui etc etc. Since being normal animes and not fantasy, It does not affect anything to add them in a crossover, since you should only add their school to the dxd world and that's it, unlike other crossover worlds as it would be with bleach, Since you would have to change the definition of death, soul, history, dimensions, worlds, energy source etc etc.