Ohh that's a good theory
I think we can all agree that the mc's dream is highly connected to mugo's past. That earthen pot reminds me from reading kekkai sensen of a ritual where the person who enacts it put poisonous bugs or in mugo's case might be snake (since he is snake god) but it would be more likely to be humans put inside the pot (just like an arc in kekkai sensen manga) and then a single being would come out of the pot as the most strongest one. Usually it would resulted the most poisonous bug. If this theory might be true that would explain why mugo has multiple personality since mugo came out of the pot as I would refer as the strongest being/victor out of being mashed/fighting other sacrifices put in the pot
Are these things the souls of the sacrifices?