Topic: So what exactly is the in-game logic behind unlocking Aria's true ending?

[Zuljaras]

It is not so weird for me the HoD 2 castle thing. When I first played the game I thought that the 2 castles are separate but certain things are connected between them. Like Maxim and the evil spirit. You change a vertain thing in one castle and the connected thing changes in the other castle.

[zangetsu468]

That's true. Yet, there are still odd situations in the game. For example, when you encounter evil Maxim and he transforms into that shadow monster. Afterwards, the only way to progress the game is to go back to the same exact room where you fought Shadow, except in castle A. Then you'll find Maxim there, crouching like he's wounded. But there's no reason why Maxim would show up in that room if you go with the "two castle existing simultaneously" interpretation. However, the developers seemed to think this was logical somehow because absolutely no clue is provided that the player should go back there. Whichever interpretation you go with, things don't add up. It's really bizarre.

Actually I don't think it's that difficult to understand, I think the technicalities are being overly thought out. Characters move in between the 2 castles, they can't be in two places at once, but Maxim can "jump" between the 2. The way this would work is in the example of the Maxim fight you've referenced; The "evil" side (B) takes over during the fight, when it gets overridden by the "good" side (A), he's back in the first Castle (A). 

However, by the end of the game, the 2 castles (layers A & B) are overlapping, hence Maxim is in both and essentially the same event is happening except that in B, you fight the evil Maxim. Which is why the good ending happens in Castle B.

However, by that token it's a game and certain events will only prompt when you reach a specific screen. This is not so disimilar to SOTN, while playing as Alucard, Maria waits for Alucard in multiple locations at one instant. Classic example being the spike room and ending room, or the Holy Goggles room/ ending room/ spike room. In reality she could only be at one of those locations, but different in game events occur in order to prompt different events to occur.

[Dracula9]

isn't it the days of future past thing where both castles exist at the same time and nothing becomes necessarily "final" in either one until one of the endings is reached

like both maxims exist at once, if you kill bad maxim the ties keeping good maxim to the castle are cut off and the thing disappears, if you kill good maxim bad maxim goes with him and everything fades because the conduit (maxim) is dead

[Nagumo]

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. 

This is not so disimilar to SOTN, while playing as Alucard, Maria waits for Alucard in multiple locations at one instant. Classic example being the spike room and ending room, or the Holy Goggles room/ ending room/ spike room. In reality she could only be at one of those locations, but different in game events occur in order to prompt different events to occur.

Could you elaborate on this? I tried looking up what you meant but I couldn't figure it out.

[theplottwist]

Could you elaborate on this? I tried looking up what you meant but I couldn't figure it out.

I think he means that, in some cases, gameplay shapes the story. On SotN, at one given moment you are able to go to two different locations where Maria is awaiting (if you do not cheat the fuck out of it, you can meet her on the Hyppogriph first and THEN on the Alchemy Laboratory later, for instance, by merely using wolf to traverse Clock Tower). She's technically in both places at the same time until you get to one of those. Schrodinger's Maria, basically. Also, the ending is the same thing: You can get a Bad Ending and have Maria never once realize Richter was being controlled.... OR you can make it so that Maria not only realizes it, but gives you the Holy Glasses. It's where you go that determines what the story is like.

Harmony of Dissonance is the similar. Your confusion seems to be coming from the fact that Lydie is in "two places at the same time" (I think, is that it?). That's not what is happening -- she's where YOU move the story next. If you go to Castle A, she's on Castle A and not in Castle B, and vice versa. Maxim seems to be the only one who is in "two places at the same time", but he has a pretty good reason: He not only IS two personas at the same time, but they are both connected (e.g. if one dies, the other also dies).

[zangetsu468]

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.

[Nagumo]

Good news: I finally figured out what what the deal is with Lydie dying in the worst ending.

When you defeat Maxim in  castle A he says the following to Juste: "Please take of Lydie for me" .... which actually is a mistranslation. In the Japanese version he says: "リディーを頼んだ" He is definitely not making a request to Juste. What he is actually saying is: "(I) have entrusted Lydie (to you)". It's not shown in the cutscene but that line is supposed to convey Maxim literally pushing Lydie into Juste's arms.

With that knowledge, it makes perfect sense why she dies in the worst ending because evil Maxim had no intention of allowing Juste to save her. In the best ending, we know that either Juste or Maxim carried her out of the castle. Earlier, I think we focused to much on Lydie being bitten or not depending on in which castle you fight Maxim.

...not that anyone particularly cared about this but it felt good solving this mystery.