Back on the lava floor at the bottom of Corrosion, with creeper spawners above the ledges and ghast spawners somewhere in the middle. It is a short one, and it ends with a wool.
Where we left off
A quick recap: creeper spawners above the ledge, ghast spawners in the middle, some safety rails already built. They split the arrows, a stack and change each, and compare chicken (17 and 27). The plan is to fill in the bottom and get rid of the lava with the water bucket, working toward the middle, since running along the bottom should make the ghast spawners easier to reach. There is only one bucket of water, so it has to be handled carefully.
The pick that got away
Five minutes in, a pick breaks, and then the chat reads Scoti_Garbidis burned to death. Something shot him while he was exposed. His stuff falls toward the lava, and the Fortune III gold pick, the brand new one, is gone. I can't believe I lost that stupid pick. He takes the back ladder all the way down to come get the rest, and borrows some wood on the way.
A spawner hides in a room they keep walking past, a ghast inside another, and ghast spawners sit on both sides of one stretch. Water goes down, the lava goes away a bit at a time, and a few more spawners go out.
Don't set off the TNT
The middle room has something odd in it: TNT. The room above the one in the middle is trapped, so please don't set it off. There is a witch spawner in there among a bunch of others, and a ladder still going up.
One room has a lot of ladders going up and a string at the bottom, which looks like a distraction set up for that trap. Then one more ladder, up from the middle, to a little room. This might be the crystal, actually. It's not. It's the wool. Run away. Victory.
Light blue
Back at the monument the light blue wool goes in, and the light blue glass lights up. They also place two emeralds from this area, 24 and 25, which means there are probably two more somewhere in there, since they cut from the top clear to the bottom instead of going room by room. Then they plan to gear up for next time.