Episode 103 opens with chores. The battlements eat cobblestone, so Basket empties a shulker box of odds and ends into a chest to make room. "We're gonna need a lot." Basket is the only player in the game; the in-game chat shows only Basket's own lines and the server's save messages.
A cobblestone run
The trip goes through a Nether portal and down a netherrack tunnel to the cobblestone storage, which sits "right before the iron" at the iron farm. Basket guesses the whole chest will fit in two shulker boxes, "plus probably a little bit extra," and fills them.
Finishing the side
Back on the walls, the plan is simple: put the same battlements on this side, finish the side that was left half done, then do "a little section on top of this thing" at the very top. This stretch has a complete corner, so it gets a stair there too. Basket also means to widen the road below a little, since the new pieces push into its space.
The inside of the wall has never been worked out, so Basket copies a pattern used once before and curls it in on itself at the corner. "Maybe we'll just chase our own tail over and over." It works on a later try. A light level check finds 8 at the lowest. The top of that small room was wood, so it becomes stone slabs, which means no cracked stone there.
The very top
The top section has an even number of blocks, so the pattern has to change. From below, one window is in the wrong spot, and Basket switches to the usual three wall pieces between openings. A stair can't sit in the corner "because of Minecraft," so the corner gets a block and a fence instead, with maybe a water spout on each side. Pillars get moved, and a ladder turns out to fit on the side of a stair. "Science. Yes."
Comparing the two sides, the windows next to the new pillars stand out, so they will have to change. Basket decides to turn them into more pillars, adds fences with torches on top, and leaves room for water to drain. "Looking good."
Trying slab windows
The old windows are just holes in the wall. Basket finds some smooth stone in a shulker box and fills one with two slabs. It lets no light in, but it looks like something. Iron bars or glass could still go in, and a viewer says it gives "a canvas to add other accents to." Wooden shutters would be nice, but the window sits half a slab off, so trapdoors won't line up.
Mirrored and checked
The other side of the top is built as a mirror, after one more trip for cobblestone. A light check turns up a dark spot, caused by one piece Basket forgot to copy. Fixed, it reads 8.
Then it's a walk all the way out of the castle to see it from where an invader would stand. "Oh man, it looks so good." Some windows still look small and odd. The next session is for the side of the keep inside the castle and the other side, where the windows get in the way of the texturing and may be moved. The credits run to the end with no gameplay after them.