On the Portraits found in game and how they detail Brauner's points on Humanity and/or current events of his time
Out of all the Castlevania games, the one I found that recieved alot of flak for it's story is Castlevania: Portrait of Ruin. One of it's most common complaints is how the story feels overall weak, with the Portrait gimmick to feature new worlds that one would never see within a Castlevania game feeling somewhat shoehorned in. However, I feel this is something that actually lends more to the story than previous Castlevanias.
Let's consider that Brauner is an artist, first and foremost. He doesn't just make paintings for fun, they're representations of how he views the world, or issues within it. Artists are products of their times, so it would make sense if all of his paintings had meanings pertaining to current events. Being at the climax of World War 2, this gives Brauner loads of material to work with. Even moreso if we consider that Brauner is the Castlevania equivalent of Victor Brauner.
The two share many similarities, namely in that they're both affected by the World Wars (Victor had to flee Paris when the Nazis invaded, while Brauner lost his daughters) and they're both surrealist artists. Look at Brauner's attacks, that is exactly what a surrealist painter would create!
Considering all of these points, it is probable to connect his paintings to worldly events going on around the times of World Wars 1 and 2, as well as towards his own personal life as well. Due to the length of this, the paintings will be set up in groups of two due to them sharing similarities: The City of Haze and 13th Street, the Sandy Grave and Lost Nation, The Nation of Fools and Burnt Paradise, and The Forest of Doom and the Dark Academy.
There is many things that is symbolic of the City of Haze. First and foremost, one could easily draw allusions to England, given the style of the buildings and the stage theme being "Victorian Fear". If we take the current events in game into account, one can easily make associations with the English pre-World War II from this stage, or at least Brauner's views of it. Originally, the English only set on sanctions upon Germany, never actually stepping in to stop their invasions of other countries. The skeletons could be seen to represent the people of England, being nothing but shaking bones in fear of another World War on the horizon. The axe armors could represent the military forces of England, who are simply wandering around and not being a threat against the upcoming nazi menace. And Dullahan? He could be seen as a commentary on pre-World War II England's status of nobility. A Knight who could help others, but his detatched head denotes that it cannot think or isn't attached to the reality of the situation. In other words, this painting could be seen as Brauner's commentary that England simply sat by and did nothing while the Nazi menace spread across Europe. Even the song name for the stage, Victorian Fear, denotes the idea of England being in fear of another World War.
As for 13th Street, we get a different look at the City of Haze. The sky is shrouded in darkness, the world is plunged into night, and there are plenty of more dangerous enemies. The evil nurse Nyx, the Blade Skeletons, Mothmen, Amalaric Snipers, Ghost Dancers and even Ghouls and Red Skeletons, and ending at the boss of the stage, the Werewolf.
Like the City of Haze, 13th Street could be seen as an allusion to England. The difference however lies in that it's more dangerous than the City of Haze. There are more people that can attack and kill you, making the whole city feel like it's in disarray. The best allusion one can draw to 13th Street is that if City of Haze is England pre-World War 2, then 13th Street represents when England was starting to get involved in it. Specifically, this stage could represent England when it was suffering from the German Air Raids. You do start out in the subway station, which is where most of the people of England evacuated to. The Buster Armors within the stage even attack with bombs! Given that we see more dangerous skeletons here, this could refer to the idea that the populace of England is now aware of the thread and is starting to fight back as well. Even the song title, "Iron Blue Intention", gets you pumped up and ready to kick ass and take names.
Even the Boss, the Werewolf, can have at least three interpretations, and one of them can factor in spite of the other two. One is that the Werewolf represents England regaining it's nobility and attacking against those who would invade it. The other is the idea that the Werewolf represents Nazi Germany, attacking like a raving savage beast across all that would harm it. The last interpretation that can play out no matter the first two is how when the Werewolf is beaten, he turns back to being human, coughing up blood before finally expiring. This scene could represent the idea that "Even the people we see as monsters are still human, with their own lives and circumstances for reaching the point they did". Afterall, many people would see invading forces as monsters, or becoming a monster to protect your homeland.
The Sandy Grave is the second portrait we come across, starting upon the desert before making our way to a grandiose pyramid, housing loads of traps, skeletons, ghosts, and enemies quite like Elgiza and Amphisbaena. As we go to the top of the Pyramid, we find Astarte, the Goddess of Fertility, Sexuality and War.
It's rather poignant that this stage is where we first meet Brauner and his daughters, where he speaks about his own motives. He states he hates humanity because they despoil the beauty of the natural world and bring it ruin. This stage is an obvious allusion to Egypt and the Great Pyramid of Giza, one of the seven natural wonders of the world. It's also poignant that the excavations of the Pyramids began in 1911, just a few years before World War 1. Considering that Brauner was old enough to have had daughters by then, it's probable that he was old enough to hear news of the excavations.
When one thinks of the Seven Natural Wonders, several emotions can result from them. The most obvious ones being wonder and awe, and an enjoyment of their beauty. The Excavations, however, took many historical artifacts and can essentially be argued as being grave robbing. This can be interpreted as "humans despoiling the natural world", taking away the beauty of the Wonder. Even the name of the painting is poignant: Brauner may have seen the excavations as reducing a natural wonder to nothing more than a "Sandy Grave". Even the Pyramid itself is simplistic, and the usage of Astarte could represent the beauty of nature not meant for mortal hands (what better way to do that than using a Goddess?). Even the song name, "Hail to the Past", could be seen as Brauner wishing to preserve the beauty of Egypt's landmarks.
On the other hand, we have the Lost Nation. We start out upon the desert at night. The full moon is a blood red, with the Great Sphinx of Giza peering down at you. Endless mummies wander the desert, and so too does a huge sand worm, but for some reason you can't find the Pyramid...unless you sink into the pit where the worm was at, after which you find the Pyramid which is completely underground.
Unlike the Sandy Grave, the Lost Nation could be viewed as the wonders of the natural world that have not been found or touched by human hands, retaining their full splendor. The pyramid is full of dangerous enemies, the world of an immortal kingdom of the dead, lead by their everlasting pharaoh, the Mummy. The name, "Lost Nation", alludes to this. The initial theme, "Sandfall", gives the feeling that this place could be just any other desert. But once we come across the underground pyramid, we get the true theme of the stage "In Search of the Secret Spell", which gives the feeling of grandeur and awe at the true state of Egypt at it's height. Or at least, Brauner's interpretation of it.
There is one other thing that's interesting to note. When entering where we'd fight the Mummy in Sandy Grave, we instead find a Persephone there. The Persephones are maids in Castlevania. This could be a Stealth Pun to how the archaeologists have "cleaned out" the Pyramids of all wonder, taking away the mummy in Sandy Grave, whereas he's still present in the Lost Nation because nobody's found him yet.
The Nation of Fools has two predominant contexts. First, many see this (as well as the Burnt Paradise painting) as representing Brauner's life. It was rightside up at first, but as he continued onwards until near the end, it all turned upside down. It could represent how his life was ruined after his daughter's demises, and how he wants to bring vengeance upon humanity and became a vampire to do so.
There is one, much more disturbing context that this troper came up with. Namely, the idea that the Nation of Fools represents Germany underneath the rule of the Nazis. The general populace of the painting is made up by cartoonish monsters, harmless and seemingly harmless. This could represent how the public of Germany have turned a blind eye to the Nazis and the threat they represent, or that they remain willfully ignorant, and as a result their apathy has lead to the deaths of many people outside of Germany. The song name, "Chaotic Play Ground" helps allude to this idea, giving the feeling of lethal playfulness while being paranoid at the same time. It's also very poignant that Legion is the boss of this area. If this painting represents Germany underneath Nazi rule, what places within Germany would have boatloads of corpses? The obvious answer: The Death Camps. Legion could be seen as a representation of Germany in World War 2, using corpses of minorities who were used as scapegoats to protect themselves from outside issues, but when the shell is pulled away, it shows what the Nazi Regime truly was: a parasitic monster.
In the end, the Portrait's name "The Nation of Fools" could basically be seen as a summation of Brauner's feelings towards Germany. On the other end of the spectrum, we have "The Burnt Paradise". Like Nation of Fools, Burnt Paradise spins around until the stage is upside down. Unlike the Nation of Fools that points inwards, Burnt Paradise points outwards, having a functional sky in place of the dark void in the Nation of Fools.
Just like how Burnt Paradise is a reverse of Nation of Fools, it equally makes sense to believe that Burnt Paradise's themes are the reverse of Nation of Fools. Instead of focusing on Germany's effects and events within their own borders, Burnt Paradise could represent the war efforts of Germany upon everyone else. It directly faces North, South, East and West, just like where Nazi Germany had seen its enemies from all directions. The place is populated with elite enemies, such as Buster Armors, Double Axe Armors, and poisonous variants of the Spittle Bone, which could represent how Germany fought through explosions, fighting to the death and poisonous gas.
At the end of the Stage, we come across the boss of the area, Medusa. She is known for petrifying those who gaze at her, and she enters by crushing statues of petrified soldiers in a snake form, before turning back into a more human form bearing a snake lower half. To this troper, Medusa could be seen as an allusion to the Nazi Regime, if not Adolf Hitler himself. A genuine snake, slitering it's way through politics and corrupting everyone through charisma. The actions of Nazi Germany have petrified the world, making them afraid to act, to which they would then crush their enemies without mercy. Even the name of the painting fits: "Burnt Paradise" is what Germany had turned Europe into, a world that once held beauty now turned into hell. The song name, "Behind the Gaze" fits because it shows how Germany was affecting the rest of the world.
The Forest of Doom is somewhat interesting in that it's not entirely a forest. Rather, it has what appeared to be an academy. However, the entire place is home to wild-life, having been overgrown with nature. In fact, it's so ruined that it couldn't even be known as an academy. Afterall, it's called "Forest of Doom", not "Academy of Doom". This lines up very well with one major consequence of the Nazi Regime: the censorship of learning and the arts. The Nazis destroyed all knowledge that disagreed with their philosophies, and destroyed all arts that didn't glorify themselves. This ruined academy could be seen as the consequences of that line of thinking, the academy losing it's status of being an "academy" and having been subsumed into the natural wildlife itself.
Another fitting event to note is that with the destruction of knowledge, it also made loads of artists, scientists, and teachers to flee from Germany. They hated what their own society did to their works, and cursed them for it. The song name, "The Hidden Curse", could be seen as an allusion to this sentiment, how they tried to curse their society but were silenced or kept their thoughts hidden.
On the flip side, the Dark Academy is the opposite of the Forest of Doom, being host to plenty of human/humanoid beings. Witches, Axe Armors, Fleamen, more beings that could be seen as sentient are here. Unlike the Forest of Doom, the Dark Academy is a living atmosphere of learning. However, this learning is not good in any case. After the Nazis had taken over and removed anything that would disagree with them and their philosophies, they started to bring forth the glorification of their philosophies, the ideals of having the strongest race and nationalism to the point of hurting others. The Dark Academy could be seen as an allusion to this, teaching dark and dangerous ideals that can corrupt future generations. And for the boss of the Dark Academy, what better way to showcase the desire to make a superior race than to have the boss be the man-made monster, the Creature?