Last time they reached the top of the building and found the wool way above it. The idea now is "a contained ladder pillar" straight up. First they need supplies, and there's a whole pile of books sitting in a chest.
The way back down
Getting out isn't simple. They came up by "crazy stairs that bypass the floors right below us," and those floors still have evokers on them. "If we were good at Minecraft we probably would have beat them up." One hallway is a dead end, another has creepers in a section they never cleared, and a moon block finally points the way. "This looks like the front door here."
An emerald out the window
Back outside, one of them shoots at a ghast and spots something. "I see the emerald!" It's only visible out a window, over where the arrow went. As far as they can tell there's one left in this section and one in the other level. The plan for that one is diamond picks and digging through the obsidian. Two things that blow up when shot sit right outside the window, but they're so close together they set each other off, and the ghast spawner under them survives.
Up the pillar
On Basket's screen the pillar goes up one block and one ladder at a time. Ghasts and skeletons fire at it the whole way, but each layer goes in fast enough that the shots barely hurt. "I'm so glad you guys can't shoot down." The rule is no following up the ladder, a lesson learned the hard way: "Get down get down get down."
Another vex
Then a ghosty guy comes through the wall, and the chat reads "Scoti_Garbidis was slain by Vex." The bed is a long way down, so Scoti digs back with a wooden backup pickaxe and finds everything, "even my super shovel." "You're gonna need your shovel when you're on your trip to hell." The levels are gone, though.
Blazes near the top
Higher up, the pillar runs into a layer of blazes, which beats charged creepers on your head. One of them gets 41 blaze powder off a single guy. "Seems excessive." There's a skeleton guarding a special blaze up there that might be a boss, and evokers below that "made tentacles come up through the floor." A torch-lit viewing platform goes in partway up so the other one can look out. One open spot lets the ghasts fire in until it gets closed.
The wool
Near the top there's bedrock. "It must mean I'm close to a place they don't want me to go to." Then a bridge goes sideways toward the wall. "I'm outside." On Basket's screen a chest labeled Wool Chest comes open. "I have the black wool." "Sweet!" "Goodbye, everything up there." That's the episode.