An entry in Fortnightly Topic Challenge #39: Deep Down in the Dungeon 1. tl;dr at the bottom
You and your wacky group of adventurers barge through a hidden door and end up in what looks to be the start of a corridor. The door slams shut behind you, leaving you in darkness. Despite your group's best efforts, it won't budge! You're stuck. You take a step forward and suddenly torches that were mounted on the walls light up, one after another in a rapid spree until you can see everything! Well, at least everything in this section of the hall. Looking to your right, you see words carved into the walls -- it reads:
Hah! You think you’re so clever
Believing you’re done at last
Well I’m eager to tell you
the worst has yet to pass
Cannot go backwards, cannot escape
Forward you go, press down a plate
Correctly guess, choose the right shape
On you’ll continue to decide your fate
A Corridor with panels and traps of killer gas
No tricking, avoiding or escaping its grasp
Keep in mind those before
And let their remains warn you
Because there’s no second chances here
As you finish reading it aloud, the group collectively outbursts in despair, "NOT AGAIN!".
What you thought might be a treasure room or an escape out of this unrelenting cave system is actually another trap. DARNIT.
Whelp, there's nothing to do but continue onward as it said. You walk down a bit and reach a pile of dead bodies...which really doesn't look promising. Looking to your left you see four square plates embedded in the wall. An Eye, a Pyramid, an Ouroboros and a Drop. 3 are pressed in, but one of them (which has a Pyramid embossed on it) is still protruding.
After some discussion, you have all decided that the 3 plates that are already pressed in must have released the killer gas and not reset. At least something is FINALLY working in your favor. You press the Pyramid plate down and something clicks....but nothing seems to be happening.
You take a hesitant step forward and aren't dead yet...so you all continue on. As you go down the corridor you find random bodies littered around in various states of decay, perhaps they tried to outrun the gas or who knows what, but they are definitely dead.
You come across another pile of bodies, with another 3 plates pressed in and another Pyramid remaining protruded. You press it in, hear another click, and continue on.
This cycle repeats a few times and you're feeling like your luck has finally changed! All these people died so you don't have to! You proceed to press in a Drop, an Eye, a Pyramid, as Ouroboros and a Drop, each with great success.
Everything is going swell...until you reach the 8th panel. Only two are pressed in. Uh oh. 50/50 chance. What are you going to choose? The Ouroboros or the Drop?
If you make it to the next section, you will find that only one will be pressed in, the Pyramid.
And if you make it past that, you'll see the end of the corridor, you'll be almost there! However...there is one more set of plates on the wall and NONE of them are pressed in. It seems you'll have been the only ones who have made it this far...so now what? Which one will you press?
Map is a visualization of the corridor. Bloody marks are where the panels are and the final panel is marked in green at the bottom.
TL;DR: Which plates need to be pressed in to get past the last three sections and why?
Hmm well what exactly is a corridor?