As you continue to hunt through the mansion of Blue Prince if you haven't been finding Red Letters chances are you've stumbled across a Sanctum Key. These 8 keys are tied to the locked doors in the Inner Sanctum, we'll show you how to get them all.
At this point you've likely already reached Room 46, but if you haven't that should be your first goal. After reaching Room 46 for the first time you can recomplete the task,and then explore the room. Inside is a document hinting of the locations of each of the Sanctum Keys, it reads as follows:
The first key found here on the furthest rank,
The second locked tight in the vault of a bank,
The third is high up, among all the clocks,
And the fourth down below, beneath all the docks.
The fifth key is held by a king on his throne,
The sixth in a station, left by one of your own,
The seventh is major if you draft it quite late,
And the last key is waiting, behind the last door of eight
For each of these keys we'll list hints to their locations before we supply you with the solutions and any additional hints so feel free to skip to the key you're after.
Note: Before we get started with this, Sanctum doors once opened will stay open, but if you get the key and can't make it to the inner sanctum then the key will return to its hiding place and you'll need to re-obtain it.
Sanctum Key Locations
The First Key
We won't go too much into the location of the key because if you've read the original riddle chances are you've also already picked up the Sanctum Key in this room
The Second Key
Hint #1 - This key is located in the Vault room
Hint #2 - It requires a special key to access it

Some tips in order to make getting this a bit easier:
- Draft the Trading Post Outer Room, collect a lot of items and the Vault (or the Coat Check) and trade a lot of items. There's a chance the vault key will appear.
- Most placed a Major Key can appear the Vault Key can show up
- The Vault can be spawned more reliably if you get the Dead End star sign in the Observatory
The Third Key
Hint #1 - You'll need to get the Clock Tower from the Drafting Room
Hint #2 - Inside the Clock Tower see if you can notice anything static or out of place compared to others
Hint #3 - Wait until 1:30pm while inside the Clock Tower
Hint #4 - Make sure you've paid attention to how to tell what memos are true, and which lie
Hint #5 - Start using the clues that you know for certain are true to block off certainties, and then work within the confines of what you have left
I.e Clock #5 must be 7pm and there must be 5 'on the hour' times
The Fourth Key
Hint #1 - This key is not in the house
Hint #2 - You'll need to drain the Reservoir fully to reach this
Hint #3 - You can use the Reserve Tank in the Pump Room if you've powered it with the Boiler Room
Hint #4 - The key is inside one of the boxes at the bottom of the Reservoir, incorrect boxes may have clues to the location of the key
The Fifth Key
Hint #1 - You'll need to reach the Throne Room
Hint #2 - The Throne Room can be obtained after completing something in the Blackbridge Grotto

The Sixth Key
Hint #1 - This key is not in the house
Hint #2 - There is another clue for this key near where Red Letter #1 can be found
Hint #3 - You'll need the pump room and the reservoir partially drained to access this key
Hint #4 - Make sure the Boat is on the correct side of the Reservoir
The Seventh Key
Hint #1 - Major isn't just a reference to this being a Major Key
Hint #2 - Late doesn't mean higher rank in the house
Hint #3 - It's lovely hearing some music in the evening
The Eighth Key
Hint #1 - The room that this key spawns in needs to be obtained via the Drafting Room
Hint #2 - Having the wrench could help making this task easier
Hint #3 - If the room can't spawn a door the number of rooms you need is decreased
Once you have all of the Sanctum Doors open then you can work on the Sigil puzzles inside.