Okay, I have to explain something before I continue the story. As you might have guessed, this story is based on the multiverse aspect and I define a multiverse as a set of universes. So, we have three multiverses, each made of 13 universes. And the old God is like the guardian of the gates of these three multiverses. The Multiverse where Saitama lives, is much like a collection of 13 universes, each like our universe, where there are certain limitations imposed in the form of Physical laws (Like nobody can travel faster than light), Only a bit loose (you can travel At the speed of light) from our universe.
I do not have to explain Goku's multiverse, because it has no restrictions and you guys know how it works. The third multiverse is a set of universes which are complete with raging wars between them. This is where our good old antagonist lies! And here's the twist, the third multiverse is connected with the other two in a way that if the third multiverse dissolves, so will the other two! But the other two multiverses are not connected at all. And so, there is a possibility to travel from the third multiverse to the other two, without going through the Old God's portals.
But this is the most interesting part, the power that the antagonist wields. I'll give you guys a hint; you can, slightly, relate it to conqueror's haki from One-piece, but, a lot deeper, stronger and a lot more… precise. Try and figure it out if you want to (you'll eventually find out anyway!).
Also, I am planning to make this a very big story, with a lot of chapters. So, I guess that's all! Sorry if you guys thought this was a chapter. But I hope you find this interesting! Thank you.