I also considered the idea that Maxim doesn't need to enter a portal and switches castle whenever his personality changes. However, It's difficult to find confirmation of this in an official source. I wish there was some kind of detailed summary of the game's story. That would really help clear up any ambiguities.
Could you elaborate on this? I tried looking up what you meant but I couldn't figure it out.
The fact that the Maxim fight directly shows the original Maxim (A) him back in Castle (A) and that he never appears in Castle (B), well the proof is in the pudding.
You could almost think of it like this - there's only one Maxim who exists between two Castles and personalities. As the game draws to a close, the Castles overlap leading to the final battle - Making it the same final battle, albeit with a slightly different context (Castle A being the physical plane, Castle B being the astral) and outcome depending on which Castle Juste entered that final room from.
Exactly what plottwist stated. Maria's location is a Schrödinger's cat scenario. She's technically accessible at all times from a number of locations, however in game time isn't real time therefore 'Real Time' which passes during SOTN's canon events, can only be prompted by the game allowing you to progress past a certain point. The exception being for example CV64/ LOD, where time is the variable which affects in game events (primarily endings or the final boss fight).
EDIT: I had a think about what you stated earlier Nagumo, about the events of Lydie's sacrifice only being prompted by one Castle, not the same room. A couple of comments regarding this:
- This supports my theory imo and what Death states about the Castle layers gradually merging at the end of the game. If Lydie's sacrifice happened in full, when it was supposed to (prior to Juste storming in), it's possible there and then the Castles would've merged and Maxim would've lost his humanity. In the end, Lydie's blood was used, but she wasn't Rondo-sacrificed (referencing Rondo of Blood's intro).
- It was mentioned the area is accessible from both castles, not one. However, if memory serves, the door itself leading up to that area from the adjacent area of that castle (B) to the right hand side (up a long set of stairs) is not accessible throughout the game until this event has taken place. I played HoD a couple of years back, my recollection being that this area is accessed via alternate means, and there's a teleportation device/ platform which allows Juste to go into both castles prior to the failed/ delayed sacrifice of Lydie being prompted.
- I believe the last fight with Maxim occurring in castle A/ B can be compared to SOTN's final battle (first castle) depending on whether Alucard wears the Holy Goggles.