This video opens with a trip back to the original area, open again, to look for whatever is still missing. A viewer's suggestion to check the letters turns up a row of symbols, the symbols open a new puzzle, and the puzzle gives up a red crystal. The crystal lights the fire under the potion pot. It ends with the fire going and the potion still not made.
Back through the old areas
"Let's go back to the original area, because now we have access to the original area." Doors that were locked before are tried again. The commentary guesses at a use for the potion: "I think the mixture I'm making potentially is going to be used to melt this thing and get that key." The search runs on hot-and-cold hints from viewers ("Yeah, I'm pretty sure I'm cold").
A torch and a pipe
The idea that gets "very warm" is the torch. The commentary remembers one spot "way over here" where "if I put this torch on something happens. I have no idea what that does," and runs there and back. Soon after: "I feel like where I just put it is unrelated," and the plan becomes getting the torch back. The other question is how to get heat into the pot: "I need to turn on the gas, where does that pipe go?" Then: "So the pipe goes into the ground."
The symbols in the letter
Then a viewer points to the letters. "Oh yes, make an excellent point, letters." The letter from the Gardens has five symbols drawn along the bottom, and the commentary remembers "a symbol like that is back in that one room." There, a keypad of carved symbols sits beside a dish of glowing orange crystals. The five go in one by one: "eyeball, circle with a T through it," and last "a backwards F."
The view swings to a round room with a cluster of blue crystals. "Aha! It's a thing I opened. I was trying to get this thing opened before."
A ring of eight lights
Next is a round panel with eight lamps in a ring. Pressing one changes others, "not the one across from it, but the other ones," and the aim looks like lighting all eight. After a good while of trying, all eight glow. "There we go, got it." The panel slides away.
Behind it is a small room with a red crystal on a box on a table. "I now have a crystal in my hand."
Finding fire
Back at the pot, the crystal goes into a brass holder beside the burner. A red beam hits the burner and it starts to glow. "So that is concentrating, and now it's lighting the fire."
Where it ends
The commentary lays out the next steps: empty the pot first, then "put all the things in there" and make the potion, "but that'll be next time." The video ends on the black pot over the glowing burner, with the potion not made yet.