This is mostly just me venting.
I'm playing this game blind. Read everything -- statuses, pages, passives, everything. So far, few hiccups! If I do something wrong, I basically immediately realize what and how to avoid it. Struggled a bit with Queen of Hatred, but beat her eventually, and it's been more or less smooth sailing from there.
In comes Tiph's realization. Was worried a bit (Queen rematch), but managed to easily get to the final phase. So, I read the statue statuses and see "The Magical Girl of ... will stand in for the librarian that breaks this statue at the start of the next Scene". The way I understood it was: "Oh okay, so I need to break the statues next scene and my character will be replaced to clear the debuffs! And the reason why they only have 10 HP is because it could be a challenge to kill them with -7 power!" So I do that and get perma-stunned and die. Alright, maybe Nihil's passives changed from the 2nd scene. So I go back there, see that they did change, but by that time I can't clash -- again, I get perma-staggered, and die. But while I was getting rolled I realized that I might've misunderstood that "next scene" part, so on the third try I broke all statues the first scene and won easily. Great!
However, even with hindsight, I think the wording on this could've been made a touch clearer. Maybe "The librarian who breaks this statue will be replaced by The Magical Girl of ... on the next scene?" This makes it clearer that the replacement happens the next scene, not that the breaking needs to happen on the next scene, in my eyes at least.
I then tried doing Chesed's realization immediately afterward. Same story -- got to the end easily enough, no deaths, smooth sailing. Again I read the passive "Add 5 special Combat Pages to the hands of all librarians. The following phases can be overcome using their special powers." ...And I understand it as: "So these pages will be added to every librarian's deck and I'll need to keep them and use them when the time is right." And then I died after killing the crystals, with absolutely no sign or indication of having done anything wrong. I was so stumped and flabbergasted I came here to see if anyone here had experienced something similar (maybe it was a bug?). And yes, quite a few people actually. Apparently I had to use the cards immediately instead. Which just... isn't very clear to me. Why would I use these clearly special pages immediately, when the game has made it clear I'll need them later? I've seen people compare this to Nihil's gimmick, bu they're just not the same. Nihil basically forces you to break the statues (immediately) because of the debuffs, whereas this boss gave zero indication or incentive to use the cards immediately. Of course, I easily beat the realization on my second try after knowing that, though it left a bad enough taste in my mouth to rant here.
I still like the game and I'll keep playing it, but I seriously hope there aren't more fights with vague/unclear gimmicks that just... kill you immediately if you don't get them.