I have said it before, and I will say it again: Eclipsa is playing all sides, because there is a monumental amount of mistrust between everyone, and since no one trusts each other, no one is communicating with each other, and now circles are being drawn in circles that is going to be everyone's downfall.
In Crystal Clear, we find out that Moon is keeping secrets from the MHC (since Rhombulus didn't know that Glossaryck had been kidnapped), the MHC keeps secrets from each other (Rhombulus' behavior to Lekmet when he reveals he froze Star, then freezing Lekmet, then asking Star to not tell anyone about anything), and -- this is the most important point -- Rhombulus freezes what his "gut" tells him is evil, without facts or evidence.
In the Song Day episode, Moon and Hekapoo are put at odds with each other because Hekapoo demands transparency, while Moon takes a stand that she had everything under control. It is because of this massive amount of mistrust that Toffee, through Ludo, wipes out the MHC and temporarily exiles Moon.
In Stranger Danger, the MHC accidentally states they don't know WHY they froze Eclipsa, other than that she married a monster, and that implicitly makes her evil. However, when pressed by Star, none of them can come up with a valid reason as to why marrying a monster deserves a punishment as severe as freezing.
In the Bogbeast episode, Moon states she did not send in Rhombulus to crash the party, meaning someone else is keeping tabs on either Star, the Temple, or something else. More importantly, Mina, with severe mental deficiencies, is as ageless as Heinous, and is aware of her existence.
In Total Eclipsa the Moon, we find out that Eclipsa has a vast knowledge of secrets that have been kept from the Butterfly dynasty that the MHC still knows about, that Eclipsa is aware of the existence of a memory-wiping spell, and that her personality fluctuates depending on whomever she is with to immediately get on their good side.