(It might go a little slow from here, as what happens within the portal might make a difference to those outside. I have a separate thread for those on inside, and might be waiting for rolls or other things. So if you are stuck in the room waiting, I apologise in advance.)

EDIT: Actually, since Sekkar and Kirin both intend to enter the portal after Rhayna, I'll just post for all three of you at the same time.

But still have to wait a moment first... 

OK, ready to continue...

One by one, in short succession, Rhayna, Sekkar and Kirin each step into the portal...

“Ok… Sure, I should be able to manage that.” Rhayna responds to Kirin. She concentrates for a moment and casts Heal on herself.

(Had other 5th lvl spells, but they took 10mins casting time. Heal is instantaneous.)

Pax says mentally, "I can also ritual cast our mental connection again, if needed. Kirin, does the maze just require any 5th circle spell to satisfy it or something specific to teleportation or illusion?" 

"If this fails, we would need to return to our previous location. A ritually cast spell would be well beyond my Banishment's limit so we would be returning to the room and face to face with the statue. A more quicker spell, should it fail to produce results I theorizes, would mean we would still have options and time for preparation should we takes the normal route of escape of this maze," Kirin replies.

(If you prefer...) At the last moment, Rhayna instead decides to target Sekkar with the Heal spell, curing him of any wounds inflicted by the statue.

Kirin was about to reply to Pax that a spell of any school would likely satisfy the maze, but Rhayna's healing spell immediately dissolves the maze around them and the group find themselves once again all together in...

...a circular chamber, about thirty feet across. The floor is black stone, engraved and inlaid with circular diagrams in silver and gold, the perimeter of each lit by magic candles. A female drow in the garb of a priestess stands in the center of one circle, hands resting on her hips. Behind her, shelves and cabinets hold ceramic pots, glass vials, and other arcane paraphernalia, while a tome bound in black leather lies open on a lectern, its pages covered in spidery glyphs. Behind the group, on the wall opposite, is an archway filled with a black void.

Looking around the room quickly Kaylyn takes it all in. She looks at the circle and she is fairly certain she knows what it is there for but just to be safe she speaks.

"Do not enter the circle and do not break it or disturb it in any way.  Gromph was known to try and summon demons.  This may be one he has summoned and it would be dangerous.  Whether the circle holds it or not let us not test it."

She tries to determine if she is correct 

Arcana 25

She also tries to determine if she can sense where Pensive may be, if he is in this room.

Kirin look arounds before seeing the tome, he moves toward, circling around the circle if needed to examine what it could be about.

Arcane? (Assuming an arcane tome) 21

Pax lifts the Gem of Seeing to her eye and looks around the room (expending another charge if necessary). 

The scratch from the statue's sword closed up (the best overkill Sekkar could think of!). The lizardman watched it disappear and then looked around in curiosity. Being completely unfamiliar with any ways of summoning (demons or other beings) he simply heed the words of those who knew what to do and froze in place just looking for physical telling signs of traps or hidden compartments, should any even exist here.

Perception: 20

(I thought Rhayna was by herself, she casts Heal on Sekkar instead. Where is the lectern?)

(everyone was dumped into the room)

"the group find themselves once again all together in... ...a circular chamber,"

(Pax and Kaylyn were together in the maze. Rhayna, Sekkar and Kirin were also together in the maze. Casting a 5+ spell ejects anyone who is in the maze into the new room with the lectern. If someone had successfully 'solved' the maze, it would have returned them to the statue room. I had devious plans of the group being chaotically split between the statue room, the maze, and the lectern room... but you've got to respect a nat 20 when it pops, right?)

The sultry voice from within the circle calls out to the group in Elvish: Finally! I've been trapped here for weeks! You have to let me out! Gromph put me in here. I tried to stop him, but he wouldn't listen, and locked me in here instead. He summoned a demon lord!

Kaylyn examines the circles and determines that they are certainly designed for holding fiends of different sizes, but could theoretically be used to trap any kind of being. It seems as though Gromph simply made use of one of the circles to trap this troublesome objector. Kaylyn still feels the emptiness that results from the loss of her connection to Pensive, and that emptiness begins slowly to fill with the heavy weight of genuine concern.

Kirin approaches the book and can see that it bears the title Zhaun’ol’leal (“The Book of the Eight” in Elvish) and describes rituals for summoning and binding powerful demons. It’s open to a chapter that talks about the summoning of Demogorgon.

Sekkar also scans the room, and finds nothing that appears to be a trap, at least not of the kind he is accustomed to. However, something does catch his eye. A huge diamond sits on a small stand atop one of the workbenches... and there appears to be something moving inside it.

Sekkar saw a very suspicious crystal but could not spot Pensive. He was not bound to the little dragon, of course, but expected him to be here. "I thought you just cleared the smoke. Did we teleport somewhere else?" If he did not hate the place even more now, it was only because the disgust reached its limit quite some time ago. "Who is in that crystal over there?" Another demon, no doubt. "And who is talking?" The lizardman squinted at the circle with the voice.

Everyone can plainly see the female drow priestess standing in the circle. It is her that is speaking. It doesn't look like there is anything preventing anyone from walking across the floor, right over the candles and circles and marks, but the drow doesn't make any attempt to step outside the circle she is standing in.

The group is certainly in a different room than the office with the desk and the homicidal statue. It seems to Sekkar that they are below the ground level of the tower, in a chamber that can only be accessed through the magic portal and maze.

Pax points at the Drow woman, "In case anyone had any doubts, she is actually a large, gross, slimy yellow tree like thing with one eye. Definitely a demon. Don't free it." 

Seeing the book, Pax nods, "Excellent, I suppose we do indeed need this book. So that this demon situation doesn't occur again. So now we can drop it into the lava and be done with it. A diamond with a creature in it? Hmmmm."  She peers at the diamond with the tiny creature it in, using her crystal.

"This is not good. This is really not good," Kirin whispers before he starts checking the lectern for any possible traps or triggers. If he finds nothing, he'll close the book and pull off off the lectern, "Ignore her for now. This is dangerous. We need to make sure it's destroyed. Some items can survive the fires of the nine hells if properly protected. Rhyana, you come from Candlekeep right? You believe they could handle disposal of this?" 

"Disposal of a book" was one the most blasphemous thing that someone could say to Rhayna. "Errr... I am not sure about 'book disposal'." She cringed at suck thought. "However, I am fairly certain that there is no safer place in all Faerûn for the book to be stored. If your concern is that no one else have their hands on it. That is." Rhayna tried her best not to snap at her new colleague. "May I take a look at the tome? Please?" She also resist the urge to just yank the book off Kirin's hand before he tries to damage it himself.

"Honestly, would much prefer molten lava. Even if that book would not burn, it would be buried there, and no one but us will know where it is. You leave it any "keep" - all the keep will know and at least one of those who know can be bought or otherwise convinced and give the book away. I say we try to destroy it." Sekkar would not trust any hiding place. They managed to get here with all the traps and drow, did not they? With enough determination someone willing to get the book can do the same. "Let's get to the labyrinth and toss it into lava!"

"Rhyana, this summoned Demon Lords,not exactly knowledge one should learn or have," He'll try to use his staff to keep the bibliophile away before talking to Sekkar, "An archmage would easily be able to find the book, should it not be destroyed by lava, with a few readily spells and we would be back at square one. If we can not confirm it's destruction before we depart from the Underark, Candlekeep is maybe most secure people to keep the book away from others. As for the keep, Candlekeep from my understand is the biggest and most fortified library-fortress, emphasis on Fortress. They would be ones bribing for the tome from other keeps. How big is the lead box? I assume this is where talisman should be and maybe we can fit the book into it. We will just tell our pesudo patron we didn't find the book,"