I have this idea after reading a fanfic.

So you remember Magnus’ speciality is memory & how Magnus uses a spell to erase his memory about Camille in TBC right? I think it’s a foreshadow, except this time, he will use it on Alec. He trades his life to save Alec, & before he die (~~NOPE~~) he erases Alec & everyone else’s memories about him, so when Alec wakes up, he will forget about Magnus & continue to live a happy life without him … BUT, because he is already very weak when he casts the spell so it doesn’t go right. Alec still forgets about him, but he also can’t love anyone else, even years after, because he feels like it’s wrong to love someone else & there is something missing. So Alec ends up alone for the rest of his life

~~MY THEORY IS GETTING WORSE. MY HOPE IS DYING ALONG WITH MY HEART WHILE WRITING THIS THEORY~~

How about in CoHF, Magnus sacrifice himself to save Alec. He is badly injured & then one of his fellow warlocks (maybe Tessa) summon his father, & ask him to heal Magnus. But even his father can’t completely heal him & Magnus went into a coma for … idk, 100 years. So Alec becomes a Silent Brother, wait & take care of Magnus while he is sleeping for 100 years. (Which also means Alec has to break the parabatai bonds with Jace, & watch everyone else die …) When Magnus wake up, he find out that he is no longer immortal & Alec once again becomes himself (just like Jem did) & they reunite & grow old together

~~At this point i can’t even think of a logical solution anymore ….. I want to write a fanfic, but I’m lazy & never actually write any fanfic before so ….~~

I HAVE THIS WILD THEORY ABOUT THE ‘DEAD BOYFRIEND’ IN COHF WAS SEBASTIAN TALKING TO RAPHAEL ABOUT RAGNOR FELL, YOU KNOW, BECAUSE AFTER WHAT HAPPENED IN THE BANE CHRONICLES I’M SURE THEY WERE DATING! And then Raphael will die in the process of revenge …

Of course, there are a lot of plot holes in this theory but ….. I JUST DON’T WANT MAGNUS OR ALEC OR SIMON DIE OK

My guess on who will die in CoHF

or more like, characters I don’t like very much & wont have emotional breakdown if they die:

1. Sebastian: obviously, the main villain. If others die & he doesn’t, i will be very pissed

2. Robert Lightwood: “At the end of #CoHF, a couple will stay separated” – Robert & Maryse IS a couple, and they are always separated somehow, so if Robert die ,they will stay separated ~~(this is just a pathetic effort of mine to deny that Alec or Magnus will die)~~And maybe he will die while trying to save Maryse (“someone die trying to save another character”), that way, others might forgive him for terrible things he did to his family

3. Camille Belcourt: I know Cassandra said she is dead, but honestly I don’t believe it. She was alive for such a long time & i dont think a new vampire like Maureen is able to kill her so easily. And I really hope she is alive so someone else can kill her in a more painful way (Alec maybe, but I prefer Magnus ~~yes I’m a horrible person~~ I dont want my baby Alec to kill anyone)

4. Maureen: She tried to kill Camille & involve herself in this whole mess I don’t think she can survive for long

5. Raphael Santiago: I can’t think of anyone else so …

6. Seelie Queen: This one is totally random. First, i realize i want to kill too much vampires, so it’s only fair to kill other kind as well. There are not many warlocks in the series (only 3 i think? Ragnor is dead already, Catarina is not really involved in this whole siatuation, and Magnus CAN’T die) so better not kill anymore of them, and I’m too attached with the werewolves to kill any of them (especially not Luke, please). Second, there is a theory about her get involved with Sebastian somewhere which I think is somehow believable, & things wont end well when you’re involve with Sebastian, & there is also that thing she did with my baby Alec so … yeah, I could careless if she die

About Simon’s “sacrifice”, i think it has something to do with his memory? I mean, that title is way too obvious & i dont think Cassandra will reveal something like that if it’s really important

So yeah, that’s my guess, and it’s pretty logical (i think???) so let’s hope for the best