Book 7 Spoilers but consider:
If potion!au somehow took place after book 7, MC would definitely be helping rescue Silver. He saved them in the dream world so I can’t imagine MC wouldn’t be at least a little loyal to him. Also they’ve experienced brainwashing courtesy of Jamil, I doubt they’d let anyone suffer under that, let alone someone they care for. With Silver kidnapped their friend, Malleus, and his guards are miserable.
And really, after book 7 no one would expect the magicless human to be helping the Briar Prince and the Dread General. MC can play the kidnapped by fae and treated terribly card thanks to Crowley and OB!Malleus, which may soften Andrei to them slightly. Who better to keep Silver away from his family than a poor child who suffered the same fate? This allows MC to befriend Silver. Meanwhile MC is reporting everything they see back to Diasomnia, and also trying to subtly jog Silver’s memory. If Andrei catches on it would look really bad for him to attack the kidnapped, defenseless friend of ‘his’ ward. In the meantime, poor Silver is confused about why a talking mouse is fretting over him in his dreams, and why that mouse FaceTimes his magicless friend through a mirror.
IDK. I just want MC to be able to thank Silver for protecting Grim and them from Malleus and his Lotus-Eater machine. I blame this brain rot on your delicious angst and that promotional line where Silver says he feels as though he has met the MC before.
TLDR: Silver is best boy so Prefect joins the save Silver team and uses their magiclessness to help him.
Thank you for listening to my ramblings, and have a great day!
(ok first things first, thank you so much for enjoying my little au??? so much so that you took the time to provide all of these wonderful thoughts and divergent possibilities??? i was so giddy when i saw this come in while i was on my work trip this week, i couldn't wait to answer it <3)
oh my goodness— i've never really considered a 'timeline' for when the potion!au would take place, but the way it would be even more heartbreaking after the events of chapter 7, ESPECIALLY with these hints that are being built up about silver's ancestors and their potential relation to lilia and malleus' own unhappy pasts??? could you imagine how raw it would feel to have silver be stolen away from them by the guards of his royal family, after he had sacrificed and suffered through so much just to bring the diasomnia family back together?? how fresh the memories of loss must be for malleus and lilia regarding the humans that they were fighting against in briar valley and the devastation and destruction they caused both to their land and to the royal family— now they must contend with the fact that silver is possibly descended from that same family, and they've all of a sudden emerged to whisk him away from the very fae that love him for who he is, not what he represents? aaaaaaaaaaaaaaa
but to your point about MC!!!! so you may notice that my fics don't really address the mc/yuu, and that's mainly because i really don't feel personally involved when i play the game, i'm mostly invested for the characters— but you bring up an excellent perspective that i've never considered! based on their journey together so far in ch7 and what we can expect to continue, i definitely think that yuu grows very close and extremely fond of silver, especially once they understand his relationship to the diasomnia clan and being part of how that plays out in real time over lilia's decision to leave their side. and i fully agree that they'd probably be one of the first to catch on to what's happened to silver, that something about him has been deliberately altered by an external force, because there's simply no way he'd abandon his family after all that he went through to protect them.
i love the idea of yuu using andrei's perception of the situation against him in order to regain silver's trust and confidence— it's beginning to play out so very similarly to how silver had to wake everyone up in the dreamworld, only this time, the tables have been drastically turned. and oh, how it hurts yuu to see him this way, to know how desperate and impassioned he was to save his father and sebek from such similar fates in malleus' dreamworld. they would certainly do anything and everything in their power to jog his memory, even trying their best to convince him to stop taking the potion that's suppressing his true memories from returning.
silver truly is Best Boy and he really does deserve a true friend in yuu after ch7 is over— who would have guessed that they would face such trials together, and bond as two humans out of place and time, struggling to realize their role in the world that they've found themselves in?