Whenever you use the Dream Nail on someone while they're awake, you only read their thoughts. And whenever they're asleep and dreaming, you enter their dreams and, on occasion, access their Optional Boss. Why? Because your mind expands when you enter REM. So the dreamer's thoughts are expanding beyond mere text as well.
One may question what kind of bug Grimm is supposed to represent, given his apparent vampire/bat theming that may seem out of place. However, he asks you to collect flames ("like a moth to a flame") and bursts from a cocoon in the Nightmare King fight, indicating he is some sort of moth.
Adding to this, Grimm's vampire-esqe design is probably based on the real world vampire moth, the Calyptra.
Why does dying to The Radiance kill you for real instead of kicking you out like every other Dream Boss? The Radiance is the original wielder of dreams, and ever since becoming an Un-person has only been able to live trapped within a dream (the Hollow Knight's), her original sphere of power. Even though she is no longer in the physical world, she's still able to affect it as seen by the existence of the Hate Plague, so it stands to reason that dying against her would kill the Knight in the physical world.
The Radiance partially resembles a moth, as moths are attracted by light. Furthermore, you learn that under her rule, insects were reduced to following a hivemind-like, basic instinct. Light triggers a basic instinct in moths and many other insects to gather around it, thus meaning that the bugs of Hallownest would follow and gather around the Radiance's light.
All those references to light Infected bugs make became suddenly clear when you learn its origin.
Notice how the Watcher Knights, the Lost Kin and the Hollow Knight all share the same sound effect when screaming. They are all physically dead and/or empty unlike the majority of the living, infected bugs, so how come they are still capable of screaming in the first place? One thing that they have in common is that they are currently being hijacked or possessed by the Radiance through the infection. So by extension, it is not them that is screaming, but that common sound effect is the Radiance's own scream.
This is further emphasized by the addition of the boss fight with an entirely void-based being, the Pure Vessel. Their battlecry is a deafening absence of noise due to being a living vacuum in physical space. This also explains why the sound cuts out briefly when The Knight is attacked; That's the sound of their closest equivalent to shouting in pain when hit.
The Godmaster update adds in a Rule of Funny content via the Eternal Ordeal Mini-Game which even has Zote humming two soundtracks. But there's quite a difference when you listen to how he hums - He seems to be putting more energy and effort in the "Truth, Beauty and Hatred" track because it's his own theme. Compare this to how he hums the Main Menu Theme, where he sounds bored and even mumbles to himself near the end. He doesn't feel like doing it because the soundtrack isn't about him.
So the Knight recovers its lost memories by hitting the black egg (where it was born) in the Birthplace with the Awoken Dream Nail. The black egg also serves as a mirror, and the Knight is using the dream nail at its own reflection, hence why the dream sequence that you get afterwards is a Pensieve Flashback.
If one notes that the dream nail's abilities are associated with light (i.e. any bug who gets hit by the dream nail while awake emits a white flash), then that scene with the Knight in front of the black egg would make perfect sense since mirrors reflect light.
It is a common phenomenon for real-life insects wherein the female bugs are more aggressive than the male bugs, often resulting to killing or eating the mates after having sex. Suddenly, this makes two scenarios in the game to have a lot more sense:
The Mantis Lords are all sisters according to the Hunter. They are the ones leading the tribe. While there exists a male Mantis Lord, it embraced the infection to acquire more power, but was driven out by the entire tribe. It can be said that the Traitor Lord was not contented with his own power, or that he viewed himself as inferior to his sisters.
The Leg Eater and Divine look like they belong to the same bug species. And after you upgrade all his three fragile charms into their unbreakable versions, the Leg Eater will climb back to meet Divine in Dirtmouth. When you do visit Divine, you can see that there is a body part of the Leg Eater lying on the ground, with the heavy implication that Divine ate him. Nonetheless, if the sexual cannibalism between bugs still applies here, one can say that the two had a mating session before the Leg Eater's demise!
There is a big fossil of a bug hanging in Deepnest that resembles a trilobite. In-story hints imply that it is one of the bugs belonging to the Ancient Civilization that existed for a long time ago.
Furthermore, when you see actual mushroom people in the form of the Shrumal, they all have a prominent orange coloration and through some NPCs, are seen to have a hivemind of their own.
After talking to Quirrel for the last time, he leaves his nail behind by the lake. While Quirrel's fate is intentionally left vague and up to the player to decide, those who believe he died might find this as a clever Call-Back to one of Quirrel's early conversations.
Quirrel: Plenty have come before us and most have met their grisly end, many more equipped than you and I. I'm sure they wouldn't mind were a fellow explorer to relieve them of their tools. It's a kindness really. The dead shouldn't be burdened with such things.
Zote's characterization is likely based on Don Quixote:
Their names ending in "-ote" might be the obvious giveway. Also, this may be just a fortunate coincidence of a Bilingual Bonus, but "zote" is an old-fashioned Spanish word meaning "stupid" or "dim-witted". Don Quixote is a Spanish work of literature.
Don Quixote was so obsessed with reading books about knights, even neglecting food or sleep until he grew physically old. Zote's shell has some noticeable eyebags on them. Both are also choleric or quick-tempered.
Having delusions of grandeur such as being a noble knight, which fuels their ego to the point where they extensively act as one. Zote even calls himself "mighty" or a "knight of great reknown".
They use ineffective equipment to brand themselves as a knight - An old suit of armor for Don Quixote, and a wooden nail for Zote.
Sancho Panza is Don Quixote's "servant" who acts as the Only Sane Man, follows and tries (but fails) to snap the latter out of his delusions. Despite his concerns, Don Quixote would often berate Sancho for not believing in his deeds. This is a parallel to how Zote treats the Knight, thinking that he is stronger and more respectable than it, even calling the Knight a "cur" when it can save him in multiple scenarios.
Believing in self-made lies just to maintain the grandeur, often making up imaginary enemies or battles. Don Quixote mistook a windmill for a four-armed giant, and claims that the "giant" experienced more pain than he did after hurting himself. Zote brags his "achievement" of taking a trophy head from the Colosseum of Fools, even if that trophy is from the weakest enemies encountered there, he's just exaggerating the facts when he returned to Dirtmouth.
Don Quixote designated Aldona Lorenzo as his lady love thinking that it is a requirement for chivalry. Later on, he became more disillusioned that someone would write tales of his adventures. In Zote's case, Bretta does exactly that, writing Fanfic in her diary that portrays him a capable Knight in Shining Armor who is in love with her.
Both lack proper social manners — Don Quixote leaves an inn without paying, while Zote ignores the Knight without thanking it as his savior.
It goes to the point where Don Quixote's neighbors mock and laugh at him for being a madman. In the Colosseum of Fools, the audience will be laughing at Zote's miserable "fighting" style.
In his adventures, Don Quixote would sometimes mention vague and imaginary, self-made stories such as the "Golden Age" of man or "the balm of Fierabras", in front of Sancho and other citizens... Like how Zote openly recites his Fifty-Seven Precepts in the town of Dirtmouth.
Don Quixote's misdeeds would repeatedly get himself beaten up by the other citizens. Zote here is a Butt-Monkey in the places where you encounter him outside of Dirtmouth, and he needs to be rescued (or you can let him be to die to the Vengefly King in Greenpath instead). Notably, the bugs of Deepnest decided to web Zote in a corner.
Don Quixote got himself arrested for freeing some galley slaves, an act that got him locked in a cage. His captors eventually set him free, but this quickly ended in a fight. In this game, Zote will get captured and caged by the Fools, but they will free him so that he could fight in the Trial of the Warrior.
Zote might have sounded it ominous, but his thirty-eighth precept is simply just describing how gravity works:
Precept Thirty-Eight: 'Beware the Mysterious Force'. A mysterious force bears down on us from above, pushing us downwards. If you spend too long in the air, the force will crush you against the ground and destroy you. Beware!
The leitmotif background music "Hornet" mostly uses the violin and other stringed instruments throughout the song, which is a meaningful Fridge Brilliance and a wise choice of instruments it itself, since Hornet is a spider and uses a stringed weapon such as silk to fight.
Silksong also reveals that Hornet can turn her needle into a makeshift stringed instrument.
What would the reasonable cause why the Pale King installed buzzsaws, spikes and traps in the White Palace? In a flashback, we see the young Hollow Knight sitting beside the King at the end of the Path of Pain route, which means that it has succeeded in the trial and proved itself physically worthy of being called the "chosen Pure Vessel".
It could also be, taking the dreamscape into account, a literal metaphor for the layers upon layers of shielding he's put up between himself and the guilt he's implied to feel over what he's done. But as The Knight proves by navigating the maze, you can't hide from your own past.
A lot of the steps towards accomplishing the best ending (at least, pre-Godmaster) involve various ways of confronting and moving past emotional pain.
To even start this trek, you need Isma's Tear, an item found by investigating the grave of Ogrim's closest friend and possibly partner. Though he clearly misses her a lot, he's made his peace with it long ago and remains as outgoing and energetic as he was when he served the Pale King.
To get the White Lady's half of the Kingsoul, you must face the Traitor Lord, who will personally kill Cloth if she's attending the fight, and is implied to have gotten his daughter killed as well, making a widow of the Grey Mourner.
To get the Pale King's half, you need to overcome the long, laborious trials of the White Palace, something that is likely to involve a lot of emotional distress on the player's part, and finding the Pale King himself dead on his throne.
To get the Void Heart, the Knight needs to take the five-notch Kingsoul, a heavy burden placed upon them by their biological parents, down into the Abyss and relive the fateful moment that set them on their course; the day they were first abandoned. The shades and most void spawn, synonymous with feelings of regret and pain, will no longer attack. Jiji's comment on summoning your now-passive shade indicates this is not just because of the Void Heart granting dominion, but because the Knight has personally overcome their own pain and has chosen to move forward.
As pointed out by this Redditor, there are rings on the Hollow Knight's shoulder pads because the "armor" was worn for the primary and intended purpose of being another binding to link chains to, and not worn as a simple armor. This meant that no matter what, the Pale King really intended the Hollow Knight as a sacrifice, regardless if it went through a knightly training.
While it may be odd to know that the White Lady Really Gets Around and cannot control her urge to breed, her situation would make sense if the player realizes that the White Lady is a "Root".
Myla's song could be interpreted as referring to either Hornet or the Knight:
Bury my mother, pale and slight
Hornet's mother is a Dreamer, so she might as well be dead, and the Knight kills her during the course of the game. The Knight's mother is a Pale Being. She's still alive, but she is "buried" in the sense that she is hidden away.
Bury my father with his eyes shut tight
No one initially knew exactly what happened to the Pale King, but it's safe to say he's not around anymore.
Confirmed by the Godseeker, who states that the Pale King is truly dead.
Bury my sisters, two by two
The countless vessels "buried" in the abyss are the Knight's siblings. Hornet's only living siblings, the Knight and the Hollow Knight, both end up dead or sealed away by the end of the game in three of the endings.
'And when you're done, let's bury me too
The Knight is "buried" in two of the endings by containing the Radiance inside the black egg. In the Sealed Sibling ending, Hornet is buried with them.
The Grimm Troupe's name could be an intentional reference to the Brothers Grimm. What do we do when we participate with the troupe? Collect flames representing nightmares. What are the brothers popularly known for? They made dark or nightmarish versions of the fairy tales that are now kid-friendly to this day.
For as hilarious as the many "child support" and "babysitter quest" memes are, it makes sense that Grimm would give the Grimmchild to the summoner-in-turn.
First, the summoner has to find the Grimmkin corpse that serves as a checkpoint for the lantern, meaning thy're an explorer who would not have objections against going around the kingdom to collect the flames.
Second, the Grimm Troupe is always summoned towards failing kingdoms, so the place is most likely dangerous; that a bug was capable to survive long enough to find the lantern proves they're strong enough to protect the child, defeat the Grimmkin, and "dance" with Grimm.
Third, who is better to go collect the flames: Grimm, a dying, sketchy and foreign bug who showed up out of nowhere in a dangerous, dying kingdom where the few survivors could mob against him in fearful paranoia; or a strong bug that everyone knows and, in the best scenario, trust already?
Four, Grimm is freaking dying when the Ritual begins to take place, he can't afford to get seriously hurt before his part begins; he most likely is gathering his last reserves of energy for the "dance" so he can (taking a page from the godseekers) "attune" to the Nightmare Heart and "ascend by ritual combat" to his Nightmare King form so his flame is fuelled enough for the child to consume and mature.
The Mask Maker says that masks are necessary for giving the wearer a "face and focus", which is weird because the Pale King's beacon already was enough to give bugs focus and intelligence. The most prominent mask owners are noticeably not real insects: Herrah (an arachnid), Monomon (a squid), Quirrel (a crustacean), and the Vessels (hollowed up corpses animated by void).
Each of the Dreamers have a character related to them that you meet throughout the game. Herrah has her daughter, Hornet and Monomon has her student, Quirrel. The exception seems to be Lurien, the Watcher, who seems unrelated to anyone else in the game. When you reach their chamber, however, you find a single husk standing in the opposite end of the room. Strangely, this is the only example of husks being in close proximity to Dreamers (Herrah is guarded by her Weavers and Monomon by her jellyfish). It behaves strangely for a husk too, not attacking Lurien despite him being one of the Dreamers keeping the Radiance imprisoned. It's commonly thought in the fandom that this husk was Lurien's attendant or butler, who stayed with him until the infection took them.
This is true. Dream nail dialogue for this unique cowardly husk refers to Lurien as its master. It is also referred to as "WATCHERS_BUTLER" in the game's files.
The kingdom's one large graveyard is the Resting Grounds. The place where us and the Knight are formally introduced to the importance of Dreams, and where we can find those who have 'slept' and become dreams.
Zote has a humongous ego, and claims to be a knight of great renown. Considering he was meant to be a playable character alongside the Knight and Hornet, it may be for the best that we cannot play as him, or we'd be proving him right just by playing as him.
Gray Prince Zote gaining more adjectives in his name as he gets stronger makes perfect sense if one recalls Zote's thirty-second precept, where he directly states that "Names have power". All of the extra add-ons to his name are causing him to grow more powerful.
Hive Knight is shown using a stinger as a sword instead of having a stinger of his own. Why? Because only female bees (i.e. workers and queens) have stingers, while males (drones) do not.
If you die while fighting the Collector, you will find that it has bottled your shade much like the other critters in the Tower of Love, likely to be added to its collection.
Since the Pale King's criteria for a Pure Vessel requires them to have no mind, nor voice, nor will, an Empty Shell with no emotions, then what does that mean for the numerous other Vessels thrown in the Abyss (including the Knight)? They could have felt emotions or developed curiosity and reasoning. With these traits, the other Vessels are aware that they are the unchosen. Imagine a child being thrown in a locked room, suffering and constantly asking itself the reason why it was rejected, and there's no one giving the answer... One could say that all rejected Vessels including the playable Knight might have experienced depression and existential crisis at such a young age.
This also makes the first two endings even bleaker than what was was shown. While the sealing of the Infection is successful, whether you have Hornet with you or not, as a failed Vessel the Radiance will eventually spill out and take control of you just like what she did with the Hollow Knight. And this time, it is highly unlikely that there will be a second failed Vessel to fix your screw up. Hornet also is unfit to be truly Hollow, meaning in "Sealed Siblings" the Radiance will escape more easily, even though you put more effort.
Every time the Knight leaves behind a black Shade when it dies, Confessor Jiji calls the shade as a "stain of regret". One could say that this has a bit of a Truth in Television when it comes to religious or occult topics. Folklore and supernatural beliefs of some countries suggest that when a person goes through a lot of mental, physical or emotional trauma, they release negative energy, that would then be unconsciously channeled and left behind in one of that person's most-used belongings. This is one of the many reasons why paranormal experts believe that restless ghosts with "unfinished businesses" are a result of a dead person's regrets or the things that they wanted to do when they were still alive but failed due to some circumstances, that regret is still present as a mark in the physical plane, mostly their prized possessions.
Likewise, some paranormal experts also believe that ghosts are stuck in the place where they last died, being trapped there and unable to move on. Suddenly, it would make a lot of sense why the Knight's leftover Shade is also idle unless you get close to it. That logic could also be said to explain why the failed Vessels or the siblings are initially trapped in the Abyss, being unable to climb back up since they're already dead.
The Journal entry for the Shade can be interpreted as the Hunter lampshading ghost phenomena:
The Hunter: Each of us leaves an imprint of something when we die. A stain on the world.
Even the Journal entry for the Siblings (which are the shades of the other vessels) also seem to support their connection to ghosts:
Fragment of a lingering will.
Up until now, the Hunter has never seen a Sharp Baldur that is so fully grown (unlike its ordinary ancestor Baldurs that can grow into Elder Baldurs). But considering how this specific species can only be found in the Colosseum of Fools, and with how their Journal entry explains them as creatures bred for battle, it is very likely that Sharp Baldurs are deliberately killed by the Fools even before they fully grow to their Elder sizes.
There are Infected foes close to the place you acquire the Void Heart. Meaning the Radiance was this close to finding and eliminating possibly the one thing that can stop her for good.
track because it's his own theme. Compare this to how he hums the Main Menu Theme