This stream of Quern picks up inside the gear building that Episode 20 opened. Two puzzles there fall quickly, and turning the building again unlocks more of it. Then progress stalls until a viewer's suggestion points at a torch holder. In the mine, an orange torch gets charged into a white crystal, which lights the building's power cells and opens a new area, Swamp Isles. The video ends at a machine there that aims a beam of light.
The clue grid
"I just figured out the, uh, sort of the rotating stuff." Turning the building's rings has lined up a window and opened a door. Inside is a board of numbered pegs that can be rearranged, a lever, and a note with six clues: "From number 5 number 3 is reachable with a knight's move," "The sum of the numbers in the 3rd row is 7," and so on down to "Number 5 is the only one standing alone in both its row and column."
The commentary sketches a four-by-four grid on paper and works through the clues one at a time, moving pegs on the board to match. "Aha, look at this, the gear is in place, game is saving." Then: "That actually was easier than I thought it was going to be."
Lights in a row
Back up the ladder, the control panel turns the building again. "Oh this might be really easy, okay, it is really easy." That opens a room where a column of diamond-shaped lights blinks out a sequence. The commentary copies it, writing the numbers down this time ("I'm really glad I did the numbers"), and a gate opens. A gear goes into place there too. Another turn of the building, and "we have unlocked the whole building."
Stuck, then a suggestion
Upstairs, a chalkboard shows symbols around a wheel. The commentary recognizes them: "these are the symbols that are on the different power cells." They go on paper, and the cells in the power station get rearranged to match. A strange key with movable knobs turns up too, and there is a torch holder behind the building that makes a noise but does nothing visible.
After a long search the commentary asks for hints, "vague hints to start." A viewer suggests that the right torch for that holder has not been found yet. The search moves back into the mine.
Orange into white
In the mine there is a lock the key fits. With its knobs set at the right lengths, it opens: "Aha! Progress!" Behind it is a machine with a torch holder and four columns of glowing rings. With the torch in, the job is to pour the glow from column to column until one is filled to a line. The commentary counts rings out loud, ends up with too many or one short, and has to repeat it in phases as the machine asks for more.
Close to ten minutes later the last phase works. The torch in the holder is now a glowing white crystal. "White is the new orange."
The power cells
The white crystal goes into the gear building, and its power cells light up, but not all of them. Some swapping follows. Two cells stay dark, and the fix turns out to be swapping the first one with another: "Okay, got it. I don't know why, but okay." The room goes bright, and the stairs up open.
Upstairs is a letter. Its writer says that after developing "the Pure White Energy Crystal, I thought that by harnessing the power of my new invention I was capable of anything." Beams of light shine at a device in the middle of the room that will not move. Nearby are three cards marked I, II and III with the numbers 70, 347 and 248.
Swamp Isles
The white crystal fits the torch holder behind the building. "There we go! That's what I wanted!" A new path opens, and the screen says "Area Discovered: Swamp Isles." A blue light along the way speaks: "this is the gift the last one who called himself an explorer left behind."
Something from the inventory goes into the top of a device, a lever gets pulled, and a machine with a large round lens opens. It turns and tilts, and the commentary aims its beam: "Oh, there's a symbol. That's cool." Turning its other parts changes the signal.
Where it ends
"I don't really know like what I want, so we'll come back to that." The video ends at the light machine in Swamp Isles, with the signal puzzle not yet solved: "That'll be it for next time."