Part 4 starts a few seconds after the last one ended. "All right, that was number seven." The party is the same, going by the nameplates: Basket, WonderSim, johnfal_92 and dash10138. The plan is to head down into the water, but there's a totem off to the right to deal with first.
A bad hallway
It's "a bad hallway," and it's full of baby zombies. Creepers keep showing up and nobody can tell where from until someone spots them coming from underneath the pillars. Somebody walks into a trap. "Not a trap anymore." Then chat reads "dash10138 was shot by Skeleton."
The room below is worse. They've been waking up spawners under them, above them and behind them, and they spend a while "fixing the problem we caused." One player explains their fire weapon: set a mob on fire, knock it back, then finish it with the axe. Someone gets poisoned. "That guy stinks." There's a nice chest at the back, and dash10138 gets their stuff back.
Seven out of nine
A bow is almost dead, so they head back up to repair and grab underwater gear. On the way the count comes up. "I thought we were at seven out of nine." Somebody else thought there were only seven in total. Nobody wrote down which ones they'd done, and the place is "too twisty" to remember.
While the others grab gear, one of them builds a diving board off the lookout. The underwater kit includes an explorer's cap, boots with Depth Strider and a three-minute potion, and Water Breathing shows on Basket's screen. "Whee!" Then: "That still makes me queasy."
Totem nine, under the water
The pool has guardians in it, plus creepers and more babies, though the babies are "not quite as annoying in the water." There's a guardian parked right by the button. Once it dies, chat reads "Totem 9 has been activated."
"But not our last totem." There's a hole in the middle of the floor that leads to whatever the totems unlock, but no totem there.
The one they missed
So they split up and look for dark spots. dash10138 points out a platform with no torches on it. One path finds a creeper spawner, another a chest that turns out to be trapped. There's a short argument about which wall is north. Then someone finds it. An elite mob blows up just as an arrow goes into it, and chat reads "Totem 3 has been activated. All totems have been activated. You can now access the inner sanctum."
Cliffhanger
"Cliffhanger. Lovely." There are about six minutes left, and the inner area could take 20 or 30. They decide to at least take a look. Everyone dumps their inventory in a chest and heads back up to the diving board.
Fall straight off and you sink deep enough to land right next to dash10138. Sea lanterns light the water. One player says there should be floating charged creepers down here. "That's exactly what you're gonna get in a few minutes. So, welcome to magenta."
"Looks like Inner Sanctum has been flooded." Then someone's internet drops. "Am I disconnected?" That's where it ends.