A_Real_Werewolf234
Although this business with Rahvdall and other worlds instantly blows up the scope of the story, this angle is pretty good. Instead of some arbitrary multiverse do-gooders or esoteric "Lord God Space", it makes a much better story for the MC to be a god's thug to go merc some other thugs and possibly recruit girls from those worlds at the same time. Of course, this should be considered in the long-term with a target of over a thousand chapters. The DXD story alone, based on the story thus far, feels like it should go to 400-500. Adding multiple worlds would hit at least 1k.
Giving a king piece to mc doesn't seems like a good Idea since he has a high chance to trigger its weakness, and the boost wouldn't be that good anyway (would only make him average satan class no matter how powerful he become) Also involving the ROB in the story is 95% of the time a Bad Idea, maybe make some side stories for it?