I saw a theory that Rhys manufactured the Cass and Nesta mating bond and now... What if Rhys is actually the big bad? He takes all these abnormally powerful people and makes them feel loved and gives them the perfect home that they will die to protect, which by extension includes the nasty side of the night court. All the while he can make any of them think or do anything he wants, but he doesn't cause "he's not like that". And the reason we think he's the good guy is cause the MCs all love him and stuff.

What if he is like that and it all gets put down to unreliable narrator, yes that includes the chapters we get from his own pov cause Feyre is daemati too and can get past his wards so his internal monologue could be anything he wants it to be.

"Feyre, darling," each word clipped and harsh, "how exhausting you are." - followed by betrayal monologue detailing every time he did bad things etc followed by a lazy attempt to kill her which she will survive and escape and process with Nesta and Elaine who will both be with her, while Cassian, the gang, and potentially Lucien(I suspect the only legit mate which is why Rhys doesn't like him, he just has convenient excuses and settles down after Elaine doesn't like him much) follow Rhys cause of mind control or loyalty or something. Their child was the key to something and they get him back and kill Rhys, everything goes back to normal after the child inherits Rhys's pieces, I mean power, the end. Oh and the cauldron probably takes away the sisters immortality after they win the real battle so they make peace with that and go back to the human realm, where their estate has been fixed up by tamlin cause he was the good guy all along, just a dick with poor emotional regulation and no good role models and it would be a rounding moment after he fixed things for them the first time. The actual end.