That jerk Mugo is the main entity....I agree. Something about keeping them at bay and he's stays in control longer adds proof ( -_・)? And I also agree with the theory that there may be a 4th Mugo and it might just be the one who needs to eat the sacrifice aka the monster
Drug addiction is no joke and it's an emotional turbulent time. Gren is just someone who lost a brother and went down the wrong path with no one to support him he's just lonely take pity!!!!
"What a conniving manipulative dictator! Why would he manipulate you like that? Why would he do that!?!?......did you give in? NO"