Gorir, ready for the stream of poison, has a hand before his mouth and nose, which helps to filter the smelly substance. He manages to keep out enough of the stuff to keep going. The stream of poison from the ceiling continues unabated, however, while Gorir stands on the second pressure plate.
Pressing the plates in the order in which they were encountered, Traubon puts his weight on the first - nothing happens. Then Gorir presses the second, and like before, a spurt of poison erupts from the ceiling, but the dwarf is ready for it and knows how to keep from breathing in the foul stuff. Then Magdalena presses the third plate.
Three thing happen at once. The door back to the throne room reopens, allowing the smelly poison to disperse. At the same time the torches that line the wall are extinguished, leaving only Magdalena's handheld torch to light the corridor.
And also the large marble door slides open, revealing a small, circular room with no other doors.
This snug room is dominated by a giant serpentine altar. The altar has been cast from copper and resembles a coiled serpent, its hood spread over a waist-high podium, stretching all the way to the ceiling. A golden bowl, dagger, and a large leather-bound tome rest on the podium.
James studies the room meticulously, all the usual spots, then the rare spots, then the impossible spots. He finds no pressure plates, no trip wires, no collapsing ceilings, no other forms of traps. Not a thing. Except - wait, that tome on the altar; there is a simple lock on it and by accident James' eye falls on the tiny needle hidden in the lock mechanism. No doubt a needle dipped in a potent poison!
When Gorir thinks about serpentine religions, his first thought is that there is a race of snake people called yuan-ti; a coldhearted folk revering the most ruthless aspects of snakes and reptiles. There are stories of a great but depraved yuan-ti kingdom in the distant past, and disguised yuan-ti trying to topple other societies in order to replace them with their serpentine way of life. As far as Gorir knows, however, those stories are mostly myths and are set in warm faraway places.
The other option he can think of is a cult devoted to some fiendish, snakelike evil, such as a marilith. The violent and chaotic nature of such a demon, however, seems at odds with the long term dealings the Baron has had with the mysterious Circle.
Magdalena jumped as the doors opened and the lights went out again. “Helm curse it!” she muttered, readying her dagger for an attack. But none came, so she eyed the room and the strange podium inside. Then she looked around for something to prop open the doors so they could get off the pressure plates.
James is pretty certain he can disable the needle with his dagger, or at least change its direction so it won't hurt anyone. The lock itself seems pretty simple and inviting to open with thieves' tools. The book might hold the information the Baron is looking for.
Magdalena looks around and the only things she can think of that can hold open the doors are their backpacks and weapons. The altar piece holding the tome might be suitable, too, but that would require getting off the plates first.
Yeah, I found it strange too that the book is open in the picture, but in the text it isn't. Little inconsistencies in this adventure.
James moves into the room and carefully takes the altar piece upon which the tome rests, and carries it back to the door. The heavy metal structure now resting at an awkward angle, the half-elf moves it a few times until he is satisfied the door will remain open.
"There we go that should do it I hope" Happy with the door James sets off to sort out that book he jabs his dagger into the lock and gives it a little wiggle careful not to damage the lock itself. Examining the lock once the needle is out the way he sets to work.
Disabling the needle trap is easy, and James manages to open the simple lock. Opening the tome, the half-elf sees pages upon pages with flowing script he does not recognize. The papyrus-like thin sheets have strange acrid smell, and each page has set of ring-shaped punctures in the lower corner.
Now that he is within the room, James sees the sacrificial bowl and dagger have obvious serpent motifs.
Satisfies that the door won't close and trap them in, Gorir goes to look at the book, taking it from James when he loses interest, Gorir tries to make some sense of the script - or at least identify what it is from.