Ok, as suspected this game has wormed its way into my brain and started theory crafting. So I know have to share. Spoilers for this and ADW
First, we can gather that this most likely takes place in the same world as ADW, due to the same backgrounds in important places like the castle, also unless Jonas and Eve have gained the ability to traverse universes and have influence in them(ignoring GD:ADW), this is their world. But that begs the question, does this take place before or after ADW, I would say after. Because while there are very slight mentions of things like the earth "god"(though I think they said mother), for the most part factions and elements seem non existent. Which is odd, because of how big a part of ADW they were, unless were here before the devs which would mean we were in the time of the old ones; which is unlikely due to Jonas. But, there is something that explains it. This takes place after ADW in the timeline where we side with the Old Ones, thus weakening the power of the devs. Now for the question of who the MC is, I have two theorys(technecally three but the third doesn't really count), one far more likely than the other.
First the unlikely one, I dont think its this one but if the Old Gods had decided to mess with him forever, we could be Ashur.
But my real theory, is much much better. We are in the timeline where the TO sided with the Old Ones, thus getting their pendant and being forced to stay whether or not they wanted to. I belieave, we are the TO. Specifically after choosing to stay. It makes sense, since if we are in the timeline where the TO sided with the Old Ones they the TO got an eternal pendant. And we know that is specifically what the MC had taken from them. More so, the MC was immedietly safe from the plauge, and was branded the Devils bride(likely after finding the pendant inside the MC that then cursed all of humanity) after having been chained to a table half their life. This suggests that the MC had been reborn already possesing the pendant in that life. To add to this, Jonas does say he gifted them(the world) you and they ruined it. Likely meaning he let you be reborn, and then all that happened. So what I assume happened is that after being gifted the eternal pendant the TO lived their life with their huge harem. But when they died, their soul could not go home due to the pendant(just what it was meant to do). Jonas also mentioned that the pendant was to stop the "gods" from ever getting control of you. Likely because being reborn would technically make you kinda one of the devs so they could control you, which was prevented by the pendant. We can also assume the stuff Jonas says in ADW about the pendant being non-romantic was a lie because he is being very romantic, where did all that "I dont date newly bornes" go huh Jonas? Now why is he doing this? Why let you be reborn and go through torture and then bless the Ashbornes? Well, the blessing of the Ashbornes was so your ashes would be safe of course. Its because he wants you immortal. He keeps talking about how its all for a far greater more selfish wish, which must be that he wasnts you immortal so you can actually be together cause dating a mortal would be akward and annoying.
Also technically we could be a third unrealated party too I guess :P.
(If you cant tell, this is now my hyperfixation. Like, as a YanStan(yandere fan club) and someone obsessed with Hot vampires, werewolves, and witches(or a scarecrow in this situation), but especially powerful kinda(or a lot) crazy gods. You have absolutly hit all of my obsseshions on the head and made something perfect for me)