The episode opens with a song: "Fish heads, fish heads, roly-poly fish heads. Eat them up. Yum." Then it's back into the aquarium with the guardians, the floating creepers and the counter at Scoti 78, Basket 73.
Plugging the shafts
The job is the same as last time. Find a creeper shaft, block it, find a spawner, break it. "When I block off these things, they die." The creepers still pop out right as a hole gets closed. "Oh, I hate when they come out right when you block it." A guardian spawner turns up too and gets taken out, and between runs they duck into their safe holes to heal.
Then one of them finds glowstone, and behind it a hallway with glass walls. "You can't put ladders on glass. That's terrible."
The trap
The hallway has tripwire across it. "How do you fix them apples?" "Shears." With the wire dealt with, they find redstone on the wall, and a dispenser loaded with a Splash Potion of Poison, Poison II. "So those would have triggered had we actually run across those things." The guess is that the creepers that were sitting in the room would have come out too.
The Brown Crystal
Inside the glass room is a chest, and in it is the Brown Crystal. It's a weapon as well as a monument block: Sharpness X, Smite IV, Bane of Arthropods IV, Fire Aspect III, Knockback III. "Are you a gambler?"
The idea of swinging it around comes up ("I need a good weapon"), but it goes back to the monument instead. Basket puts it in the Brown slot, and the chat reads "Congratulations! You have defeated: HELICIAN LABS." That's 13 of 16 crystals, with Green, Red and Black still empty.
Scoti_Garbidis brings an emerald block over, and the ninth slot fills. "The ancient gods have sent you a present." The present is a chest of gold and The Punisher (Level 2): Sharpness X, Smite III, Fire Aspect II, Knockback II, and Unbreakable. "True justice knows no mercy."
Reeking River
The next sign says it plainly: Green Crystal, Area: Reeking River, 9 Emeralds. They head down a jungle path, and a few steps in, the chat turns red. "An Elder Witch has cursed you. You must kill the Elder Witch(es) to remove the curse." Weakness IV and Slowness. A sign spells it out: "Your arms feel weak and your legs feel slow." Then: "Who could be casting such powerful evil spells?"
Swords are no good with Weakness IV, so it's bows. The Elder Witch keeps drinking health potions. "She's been eating her Wheaties." Infinity on both bows means they can keep shooting, and eventually it works: "You are no longer cursed." "Oh man, that's how this whole level is gonna be." The next sign agrees. "Now that she is dead, the curse is lifted... but what if there are more elder witches out there?"
Gaia
Further in, there's a chest with a sign on it, and above it, a glowing green thing with the name "Gaia." "It says important lore." That's where they stop, with the lore unread until next time.
Nobody dies. The counter ends at Scoti 78, Basket 73. Crystals are at 13 of 16 and emerald blocks at 9 of 12.