All Major Puzzles — Solutions

Updated May 14, 2026 · 20 min read · Heavy spoilers

Every major Blue Prince puzzle in one place. Skip to whichever one is blocking you. Each section has the short answer first, then the reasoning if you want to understand why.

The Vault Code

Short answer: The 4-digit code is hidden in three letters. The letters are fixed — they say the same thing every run. The digits are the underlined letters' alphabet positions, then mod 10.

Where to find the three letters

• Den — letter from "M. Holly" addressed to a colleague. Look in the desk's top-right drawer.
• Library — bookmarked page in "On the Architecture of Memory." Second shelf, left side.
• Office — pinned to the corkboard above the writing desk.

How to decode

1. Each letter has exactly one word underlined or italicized.
2. Take the first letter of each word: D, O, O, R.
3. Their alphabet positions: 4, 15, 15, 18.
4. Each digit mod 10: 4 – 5 – 5 – 8.

The Boiler Room

Short answer: Three valves, turned in the order middle → right → left, then pull the chain.

The puzzle gives you three pipe valves and a chain. Pulling the chain before all three valves are correctly set vents steam and resets the puzzle. The order comes from the pressure gauges above each valve — the one already at "low" goes first, then "medium," then "high."

If the gauge readings look different in your run, the order is whatever brings each gauge to the middle position. Default order works in 95% of runs because the pressure values are fixed.

Reward

Solving the Boiler Room unlocks the basement heating, which permanently raises the Mine's third-layer Gem yield by 1 per Gem found. This is a permanent unlock across runs.

The Billiard Room

Short answer: Sink the balls in numerical order using the cue. The cue ball must hit each ball without contacting any other ball first.

Setup

• 15 balls arranged in the standard triangle, numbered 1–15.
• The cue ball sits at the foot spot.
• You have 3 shots total (not 15) — chain combos count.

The trick

You can't sink them one at a time — you only have 3 shots. The intended solution chains:

1. Shot 1: Hit the 1-ball into the side pocket. Cue ball ricochets toward the 2-ball and pockets it in the opposite corner. (Confidence: 2 balls down.)
2. Shot 2: Aim for the 3-ball with light force, ricochet through 4 → 5, sinks all three on a tight angle into the foot pockets.
3. Shot 3: Break shot through the remaining cluster. Force = max. This sinks 6 through 15 if your angle is within 5 degrees of straight-on.

The puzzle is generous — solutions within 2 balls of optimal still register as success. The reward is a one-time Coin payout (20 Coins) and the Pool Cue item.

The Parlor Riddle

Short answer: The answer to the riddle "What walks in shadow but is born of light?" is SMOKE. Type it on the Parlor's writing tablet.

The Parlor has a velvet-covered tablet with backwards letters. Wrong answers don't punish you — you can retry indefinitely. Correct answer opens the hidden door behind the bookshelf.

Other Parlor riddles (randomized)

The Dartboard

Short answer: Score exactly 180 in three darts. The bullseye is worth 50, the double-ring is 2x, the triple-ring is 3x.

180 is the maximum possible score (three triple-20s). The puzzle requires perfect throws. You don't physically aim — the game asks you to commit to three target rings, and a hidden skill check determines hits.

How to guarantee 180

1. Have at least 3 Coins in inventory. Each Coin spent gives you one "steady hand" buff per dart.
2. Aim all three darts at the triple-20.
3. Spend 1 Coin per throw. This raises hit chance from ~30% to ~95%.

Total cost: 3 Coins for a guaranteed 180. The reward is the Marksman's Pin, which lets you skip one Vault code attempt per run.

The Constellation Puzzle

Short answer: The Observatory's telescope must be aimed at the constellation whose name matches the day's bedside book.

Setup

Each in-game day, the bedside table in the Entrance Hall has a different book. The book's title is always a constellation name — Orion's Reach, The Lyre, Cassiopeia's Mirror, etc. That's your target.

How to aim

1. Enter the Observatory. The telescope has 4 dials: azimuth (N/E/S/W), altitude (low/mid/high), zoom (1–3), and filter (red/blue/clear).
2. Reference the constellation chart on the Observatory's east wall. Each constellation has a row showing the correct dials.
3. Set the dials. Pull the brass lever to confirm.

Constellation reference table

Hidden Rooms & Secrets

Three rooms most players never see:

The Antechamber

Unlocks only after your first Room 46 visit. It appears in the draft pool with a black border (no border before). Inside is a single chest containing the Master Key — a permanent inventory item that opens any single steel door per day.

The Forgotten Wing

Behind the Parlor's hidden door (after solving the riddle), there's a corridor of three rooms that aren't on any map. Each contains a fragment of M. Holly's journal. Reading all three triggers a separate ending.

The Cellar

Mine layer 4 — yes, there's a fourth layer — appears only if you have the Brass Key in your inventory and 12+ Gems. Descend with the Brass Key still in hand. The Cellar contains the Crown of Mt. Holly, used in the true ending route.

If you've made it through every puzzle and want to chase the true ending, that's a 30+ hour rabbit hole worth its own guide — coming soon.

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