High Peak Castle

"High Peak has fallen from its former glory... The last banquet held here served up human flesh."

Last hurdle before the final boss, High Peak Castle is a magnificent building set on a linear flow, where the player must traverse its halls filled with statues, banners and paintings to collect the keys from the Elites found in three specific areas to open the gates to the Throne Room. The Elites will always be a Slasher, two Trackers (fought at the same time) and a Thorny. At the start of the area the player is greeted by a gigantic statue of the King of the island. The various rooms containing the Elites with the keys are engulfed respectively in a red, green and blue light, and have props already seen in the Ossuary, the Promenade of the Condemned and the Slumbering Sanctuary.

Only two keys are required to get to the Throne Room, the third key will lead to a room that contains a Scroll of Power, two randomly generated items and the Blueprint of the Boomerang, that requires the Spider Rune and a very tight parkour over spikes to get to (however it can be done without the Spider Rune, but an amulet with an Affix that grants multiple jumps is required). Alternatively, if you've unlocked it, the Homunculus Rune can be used to grab it at very little risk.

General lore
The Castle hides a number of lore rooms shining light upon the events that led to the downfall of the King and his court, as well as the whole Island.
 * "The royal guard stayed locked up safely behind the walls of High Peak Castle, thereby leading the island to its ruin."
 * "High Peak has fallen from its former glory... The last "banquet" held here served up human flesh."
 * "The island's high-ranking personalities came here to discuss important issues with the King. The quality of the visitors has changed a lot in recent times."
 * "The King allowed the Alchemist to move into a wing of the castle. That was around the time of the final retreat."

The rotten corpse of a soldier is found next to a stained letter he wrote describing his symptoms. He was coughing blood, his body was so itchy he scratched himself until he bled, had headaches, blurred vision and felt down.

Elite rooms
Three Elite rooms can be found, each having its own design and Elite enemies.

The Alchemist's Room
The blue room appears to have been a laboratory for the Alchemist, granted to him by the King as a last resort option when he realized his ruthless methods were not working. Indeed, its shelves are full of various potions, vials and general scientific equipment akin to the various labs the Alchemist left all over the island. In the center of this room, where the Beheaded fights an Elite Slasher, endless rows of incubators can be seen, filled with mutated bodies. They are the same as those found in the Alchemist's Clock Tower lab, in which he was immersing infected bodies in an experimental solution in hopes of finding a cure to the Malaise.

It is unclear whether the Slasher enemy was a result of the Alchemist's experiments or if it is just another Malaise-infected character, but the fact that it is the Alchemist's Room boss suggests it could be the case.

The Human-Plant Room
The green room is host to a variety of plant-like structures, and its walls, floors and ceiling have been colonized by vines. In the center of this room, the Beheaded fights an Elite Thorny in front of a hybrid human-plant character who seemingly broke out of its incubator. This hybrid is the result of crossbreeding experiments by the Alchemist, in which he tried to administer plant extracts to a human "volunteer".

While the Alchemist reports that the experiment was a failure and that the subject did not survive, the fact that the incubator is broken and that the room has been invaded by plants suggest the hybrid did not actually die, and wreaked havoc in this part of the Castle.

It is unclear whether the Thorny enemy was a result of the Alchemist's experiments or if it is just another Malaise-infected character, but the fact that we fight it in this room and that the spikes on its back resemble the thorns of a rose (from which the hybrid seems to have sprouted) suggest it could be the case.

The Torture Room
The red room appears to have been a torture chamber, as evidenced by the various torture instruments scattered on the floor and hanging from the ceiling. In the center of this room, the Beheaded fights two Elite Dark Trackers in a pool of blood flowing from a fountain, with what appears to be dismembered bodies and skeletons hanging from the ceiling.

There is currently no lore in the game explaining the purpose of this Torture Room. It is unclear if it was used before or after the Malaise outbreak and the Island's downfall.

Trivia

 * As of the Baguette Update alpha, the paintings in the Castle depict the various NPC's of the game, such as the Tutorial Knight, the Collector and others:
 * There is a painting of a mariner with tentacles for limbs and one red glowing eye hidden under a hood. This character was an NPC, now removed, found in the Pier with the purpose of announcing the player that "your vessel hasn't docked yet" as to intend that there is currently no content after the Pier. He would've then proceeded to kill the player with one of the Watcher's tentacles, effectively counting the run as completed.
 * A painting of the island Dead Cells itself takes place on is present.
 * There are also many paintings with easter eggs and references to other games such as:
 * A parody of the famous painting The Scream.
 * A portrait of Alucard from Castlevania: Symphony of the Night.
 * A portrait of the main characters from Nier: Automata.
 * A portrait of the main character from Hollow Knight.
 * A picture of a bonfire with a curved sword embedded in it, clear reference to the bonfires from the Dark Souls franchise;
 * Landscape paintings of the Obsidian Woods and Magaari Ember Highlands, from the game Duelyst.
 * A landscape of a firewatch tower, in similar style to the game Firewatch.
 * The titular sword from the game Transistor.
 * A painting of a boy walking into a culvert/cave, from the Netflix series Dark.
 * A painting of the Estate from the game Darkest Dungeon.
 * A picture of Solaire of Astora, character also from Dark Souls, in his trademark pose "Praise the Sun!".
 * The fact that there are paintings of characters from the franchises of Castlevania and Dark Souls is probably a joke about Dead Cells being a metroidvania (game with the level design of Metroid and Castlevania) that shares a similiar combat system with Dark Souls.