
From what i underatand, the mirror is like another dimension/portal where seth’s wife (i forgot how to spell her name) got trapped. Not her entirely but a part of her soul/emotion (her love for seth) got trap and what comes out of the mirror is a shell of herself. So what seth assumes happened to her also happened to Horus (where he got manipulated to THINK he loves Seth)—this is what Seth believes and now doubts what Horus’ intentions truly are (this is my understanding—someone who may know the mirror better please explain/correct me!)

The mirror was a gift from ra to hathor and there are 2 of them. It has magical capabilities such as if u look into it and there's someone else looking at it from other side, then you'll see their reflection n fall in love with them against your will. If there is someone u alr love then the mirror will rip u in pieces and the part of u that loves someone else gets locked up forever in mirror void while outside u is incomplete but reset version who now loves the person reflected in mirror.
2. If the person reflected in mirror is same as person in your heart then u wont be trapped you'll be able to leave void but temporarily you'll be under mirrors magic influence n it'll heighten your deepest desire so badly that you'll act them out against your will.
Osiris wanted to use it on seth n snuck it in among his war spoil gifts but neph accidentally gazed at it. She fell in love with osiris n since Her deepest desire was to have seth's child (osiris stole Seth's sperm unbeknownst to them) she went to osishit n begged him to have a kid with her. The part taht loved seth was locked inside mirror all these centuries since then until ch 186 when isis finally notices shi n rescues her from mirror with help from sekhmet
Hathor wanted to do the same to horus but seth was messing around n his gaze was what horus saw in mirror but horus alr loves seth so he wasnt split or trapped but under magic influence he raped seth against his wish when seth had crept in his bed to rape him in s1.
Breaking the mirror does nothing cuz neph isnt inside it anymore. Horus knows this but seth doesnt know which is why he attacked horus like this.

Youre correct ^^. Osiris riddled seth with so much insecurities n deep rooted fear /doubt that even falling in love with horus - something that finally seth did on his own without any outside manipulation (like his sham marriage to neph as orchestrated by osiris) was a big step forward in his character development but when hathor revealed neph's condition n said horus was suffering the same ( she doesn't kno horus alrdy loved seth in his heart lol so she thinks horus is also bewtiched) seth instantly fell for it cuz of his crippling insecurities n self hatred. He mumbles ofc who'd fall for someone like him n is absolutely devastated n wanted to run back to neph even tho he doesnt love her anymore because she is nostalgia n familiarity someone he thought he wouldn't be able to hurt him the way he feels betrayed rn. He is more hurt by the fact that horus love is fake than the fact of horus hiding neph's secret Σ(  ̄□ ̄||)
lowk forgot, idk if anyone had alr said this but if anyone could pls tell me that would be great TT thank you!