High Peak Castle

Access and exit
High Peak Castle is can be accessed via the Clock Room, Guardian's Haven, or the Mausoleum.

The exit is blocked by two locked doors that need a each, which can be found from the Elites found in three specific areas to open the gates to the Throne Room, where the Hand of the King awaits.

Colored rooms
High Peak Castle will always have three rooms where Elite enemies reside. These Elites will always be a Slasher, two Trackers fought at the same time, and a Thorny. The various rooms containing the Elites with the s are engulfed respectively in a red, green and blue light.

Of the keys that they drop, only two 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. Subsequent runs after the blueprint has been obtained will contain an item instead.

Scrolls
High Peak Castle contains 2 Scrolls of Power, and 2 Dual Scrolls. When 3 Boss Stem Cells are active, this biome has 1 guaranteed Scroll Fragment, and when 4/5 Boss Stem Cells are active, this biome has 2 guaranteed Scroll Fragments. These cannot spawn in areas requiring the use of any runes.

Enemy tier and gear level scaling
In the table below, you will find the gear level and enemy tier of the High Peak Castle based on difficulty.

Main level

 * 1 Treasure chest behind
 * 1 Treasure chest behind
 * 1 item behind
 * 1 item behind
 * 1 item behind
 * 1 Weapon shop
 * 1 Skill shop

Castle Keys
The blueprint for the can be found next to the exit to the Throne Room and requires the 3rd Castle Key. The player needs the and the  to go through a very tight parkour with spikes. However it is also possible to do without the Spider Rune, but an amulet with an Affix that grants multiple jumps is required. Alternatively, the can be used to grab it at very little risk.

Moonflower Keys
The blueprint for the mutation (3+ BSC) can be found in a secret area where the player must have 3 s. These keys must be obtained by exchanging the s from the Promenade of the Condemned and going through the Ramparts, the Graveyard, and the Forgotten Sepulcher, where the keys will be hidden throughout each level in secret areas.

Enemy blueprints

 * The blueprints for and  (4+ BSC) can be looted from Lancers.
 * The blueprints for and  can be looted from Guardian Knights.
 * The blueprint for can be looted from Royal Guards.

Enemies
The table below lists which enemies are present in the High Peak Castle on each difficulty level and which blueprints each may drop. When applicable, the minimum difficulty level for blueprint acquisition is specified.

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 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, suffered headaches, blurred vision and felt down.

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 in the Alchemist's Room 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.

Destroyed lab
In the castle is a lab destroyed by the king's loyalists, all of which criticize the Alchemist's efforts for creating a cure, and that isolation is more effective:
 * "The desk was ransacked."
 * "Someone wrote in the diary, over the notes of the "alchemist", as he called himself."
 * "Why do you continue your experiments, you poor fool?"
 * "We have to stand together in the face of adversity."
 * "We have to ISOLATE healthy people from those affected by the Malaise!"
 * "LONG LIVE THE KING!"

Abandoned chamber room
Inside the castle, a room with multiple beds can be found, presumably the quarters of the room guard, including the Hand of the King's. A note from a guard can be found, noting how the hand is above the King's suspicion and wishing well for the Giant as they haven't seen him in a while:
 * "The Hand is above the King's suspicion, which is more than I can say for the Giant... Though I secretly hope he's ok, we've not seen him in a while now."

Another note from a guard notes how the food tastes different since the king ordered the old cook executed:
 * "There's a strange taste to the food since the old cook was offed. The Hand doesn't seem to mind though, so I just hold my nose and dream of custard."

A note from the Hand of the King explains the King's paranoia of a plot again his life:
 * "The King is convinced of the existence of a plot against his life. While such a plot may have cause to exist, I've seen no evidence of it. Worse, the food hasn't been up to standard since he had the cook executed..."

Additionally, another letter can be found next to the Hand of the King's bed, mentioning how the king took down the portrait of him and the Giant personally, and how his men were rattled:
 * "The King came to my quarters to personally remove the portrait of the Giant and I together. I understand his frustration, but my men were rattled..."

Trivia

 * In earlier versions of the game, this biome was just named The Castle.
 * The paintings in the Castle depict the various NPC's of the game, such as the Tutorial Knight, the Collector and others:
 * A painting of the island Dead Cells itself takes place on is present.
 * A room bigger than the usual with a giant painting of the Giant when he worked as a royal guard for the King.
 * There is also a painting of a mariner with tentacles for limbs and one red glowing eye hidden under a hood. This since-removed NPC was the Fisherman, who could be found in the Pier biome. He would say to the player "your vessel hasn't docked yet", indicating that there was no further content beyond the Pier at that point in the game's development; and would then proceed to kill the player with one of Conjunctivius's tentacles, effectively counting the run as completed.
 * There are also many paintings with easter eggs and references to other media. These include:
 * 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 Knight, main character from Hollow Knight, another Metroidvania-type game.
 * 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 reference 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!".
 * A picture of Stilgar, from the 1991 game Dune.