MxB is the pairing of The Mirror Isles with the Vault of the Beamcasters. Finding its gold room is a common question on the Steam forums, and only about 7% of Steam players have opened it. Its areas, Reflected Beams and Beams Reflected, put the Trader's mirrors on the same boards as the Vault's beams.
Reflected Beams puzzle 2. The Trader stands beside a mirror on a stone platform over dark water, with more platforms to the right.
How to reach the MxB gold room
Players on the Steam forums point to two routes. Neither needs the Endgame.
- From the mirror side: use a mirror a little down and to the right of the red floor area to reach the room. Another player points to a mirror at the end of the ice area that leads to a second mirror in the corner.
- From the beam side: keep extending the green beam to the left, starting from the first room of the Vault of the Beamcasters.
A common trap: in the west-side Red Room, only the right-facing purple beam is locked behind the Endgame. You can power the left-facing one at any time by moving the gem. One player only spotted this after unlocking the Endgame.
These directions come from players, not a video, so treat them as pointers rather than exact steps.
Achievements
| Achievement | Unlock | Steam global % |
|---|---|---|
| Gold MxB | Open the MxB gold room. | 6.8% |
| Antipode MxB | Activate the MxB teleporter to the Antipode. | 2.1% |
Rates as of 12 October 2026. The full list is on our achievements page, and the teleporters are explained in the Antipode guide.
What to expect
- Mirror rules from The Mirror Isles still apply. Using a mirror teleports you to your reflected position, and mirrors can create clones. If you need a refresher, read our Mirror Isles page first.
- The beams follow the Vault's colour rules. The Vault page has the colour table.
- Puzzle 6 of Part 1 is the longest, with nearly three minutes of solution. Puzzle 7 is next at over two minutes.
Reflected Beams puzzle 6, one of the longest. Red beams cut through a maze of hedges and red blocks.
How to use the tables: "Starts at" is the point in the solution video embedded lower on the page where that puzzle begins. "Solution length" is how long the finished solution runs in the video, which is a rough guide to how long the puzzle is. Puzzle numbers follow the video's order, which is the order the player solved them in, not a number shown in the game. You can also jump straight to any of these puzzles from the Puzzle Finder.
Reflected Beams: puzzles 1 to 13
| Puzzle | Starts at | Solution length | Notes |
|---|---|---|---|
| Puzzle 1 | 0:00 | 1:24 | |
| Puzzle 2 | 1:24 | 1:04 | |
| Puzzle 3 | 2:28 | 1:13 | |
| Puzzle 4 | 3:41 | 0:33 | |
| Puzzle 5 | 4:14 | 1:26 | |
| Puzzle 6 | 5:40 | 2:56 | The longest. |
| Puzzle 7 | 8:36 | 2:21 | Second longest. |
| Puzzle 8 | 10:57 | 0:45 | |
| Puzzle 9 | 11:42 | 0:42 | |
| Puzzle 10 | 12:24 | 0:38 | |
| Puzzle 11 | 13:02 | 0:50 | |
| Puzzle 12 | 13:52 | 0:30 | |
| Puzzle 13 | 14:22 | 0:47 |
Reflected Beams: 3 more puzzles
The uploader missed these three puzzles in the first video and covered them in a short second video, which numbers them 1 to 3.
| Puzzle | Starts at | Solution length | Notes |
|---|---|---|---|
| Puzzle 1 | 0:00 | 0:35 | |
| Puzzle 2 | 0:35 | 0:26 | |
| Puzzle 3 | 1:01 | 0:33 |
Beams Reflected
The second MxB area is called Beams Reflected. There is no per-puzzle solution video for it so far. The only full recording we found is Mikan Hako's blind playthrough, which runs about an hour.
Solution videos
Sources: route directions from players in the Steam discussion thread on reaching MxB. Achievement rates from Steam. Puzzle lists from The Flying Chungus solution videos. The area names come from Mikan Hako's playthrough series.