Erm...

I second this

In the season 1, Horus saw Nepthys locked up. Now they’re meeting again. This time they realize locked up Nephtys is a part of her memory in which she loved Seth. We can assume Osiris somehow managed to trap that memory and made Nephtys had an affair with him. So that Seth would have no choice but go to Osiris. Is what I gather so far. But I don’t get the involvement of Sekhmet and the other black haired goddess.

Hii half part of what u said is true. Continuing to that..
you see there are 2 mirrors with magical properties, one is hators and one is sekhmet.
One of their magical powers include making someone fall in love with the person they see in the mirror. Now if the person they see is not someone they already love then the part of them gets stuck in the mirror and the one outside is an incomplete person whose memories are wiped clean so that they love the one they saw in mirror. So nephyths loves Seth but she saw Osiris in the mirror so the mirror captured her memory- the part that loves Seth inside and the one outside is bewitched to have affair with Osiris and fulfill her deepest desire (she wanted to have Seth's baby because she loved him :(

Horus wasn't captured and left freely cuz he saw Seth in the mirror and he alrdy loves Seth so there was no reason to keep him trapped but the mirror also amplified his darkest desire so we saw that rape chapter of horus n Seth.. he would never willingly do that otherwise. That mirror was given to him by hathor so that he'd fall for her but he saw Seth in it. Osiris also put that mirror among Seth's gift with similar sinister intentions

Ooooh that makes so much sense!! Thank you I was so lost ngl. Even for the rape at the beginning, I didn't understand it but now I do. Yay!!