The reason Mugo is split into three is cuz smth happened to Jaheon( i suppose in the Joseon era from the looks of it?) That is probably related to that jar we saw in the very beginning of the story.
I'm calling it forbidden romance gone wrong plus the failure to protect made Mugo turn into a evil/malevolent spirit thus not being a real god OR good God falls for a human, fails AND THEN turns evil.
Most definitely Jaheon's death was not by natural causes AT ALL.
On to the mysterious jar bit, one of them was locked inside the jar and both died thus making either way Mugo lose his marbles.
He probably made the pact to help that family expecting Jaheon to come back to life someday and for that reason he killed the previous lunas.
Since the three mugos are part of one being I'm guessing each one has a core memory related to Jaheon and the original being that they are(oh and I'm saying other core memory besides the one of losing him once)
Those are my bets so far



If yall didn't see it coming then you're really innocent. Hunter crash out after yujin left was everything I needed to know. Anyone who read about a certain lawyer and his crazy mob bf know what I'm talking about.
Miss korea went through a lot ( ̄∇ ̄")
The only thing that is saving him is that they're freak4freak lol