Squiggles makes a flourish and a bat appears from nowhere(his familiar). "I suspect your logic is correct Jarl, but let's see what Fluffy can see". 

Squiggles telepathically tells Fluffy to go down the left path and report on it

Fluffy flies up the left path, which winds around a few times over a few hundred yards, before coming to an end. Based on the way Fluffy's sonar bounces off of it, (s)he(?) senses that a part of the end wall of the passage is made of a softer material than the surrounding stone. Wood, perhaps. Likely with some metal embedded in it. Seems rather door-like, come to think of it.

Squiggles signals Fluffy to come back.

"Jarl, I can confirm your hypothesis I believe. Fluffy found a wooden door up there"

OOC: Did Jarl’s 27 Perception Check reveal anything before we proceed?

     "It may be worth checking out that door. Our path behind us through the undercroft is locked and if we need to make a hasty retreat it would be good to open an open way out of this place."

"Leave it to me, my friend, although I do hope this door doesn't give us as much trouble as the last one."

Balian squeezes through the crowd and slinks silently up the passageway towards the door.  On reaching it he examines the door and its surroundings, along with the lock, and presses his ear to it to listen for anything on the other side.

Perception: 18

Investigation: 15

Flynt Silverfalcon quietly made his way down the cave corridor several feet ahead of his companion. The dragonborn came across a group of adventurers and quickly introduced himself. "Good day, I am Flynt Silverfalcon of the Silverfalcon clan. My companion and I are searching for the Mabaran Resonator. Perhaps you have heard of it." 

Balian hears two voices through the door, getting louder. Suddenly he is knocked backwards as the door flies open and a pair of dragonborn burst through it. (cue Flynt, above) 

Squiggles hears the door open loudly and goes on alert, using Minor Illusion to create the sound of a Carrion Crawler up ahead as a distraction to help Balian

As the door is shoved open with considerable force from the other side, Balian absorbs the impact and uses it to put some distance between him and the door, sliding to a stop as his hand instinctively draws one of his shortswords.  Seeing the two dragonborn enter the tunnel, and one address him rather politely, he relaxes slightly, and lowers his sword.

"Well you don't look like angry spirits or animated suits of armor, so I guess you'll do.  An aarakocra send you down here too, by any chance?  If it did, it didn't mention any resonators to me or my companions.  It's restless undead and the possibility of possession by an aboleth for the likes of us."

Hearing the sound of a monster over his shoulder, he turns and shouts back down the tunnel.  "Squiggles!  Knock it off! Trying to have a conversation here!"

Addressing the dragonborn who spoke to him, he thrusts out a hand and continues, "Balian Ibelin, at your service!  We might make use of each other tonight, so follow me and meet the others."

With that, he turns and makes his way back to the rest of the party.

Flynt shakes Bailan's hand. "That sounds fair," he says as he begins to follow him. 

   "Uhm... Actually, Bailan, our birdie benefactor did, in fact, mention the aboleth may a have of a resonator that's making the dead restless. Though I don't think he named it as such." Shale lights up his staff again to get a better look at the newcomers. "Hmm... Dragonborn. A pair no less." The earth genasi begins looking back and forth, holding his staff high so that the light from his staff can be more effective. "Has anyone seen our goblin? Brix!? Where the hell's did you get off to?"

“He did use the word resonance, but Mabaran, that I’m not familiar with. Is that where it comes from?” Jarl steps into the light enough to be seen, but no more, his hand still on his quarterstaff.

"Hello everyone! Pleased to meet your acquaintance, I am Celric, I am but a humble servant of Bahamut, and I know that his divine guidance have led my partner and I straight to your surely very powerful and righteous group, surely you all have heard tale of Bahamut... here..." Celric, the golden heavily armored dragonborn, puts his shield on his back while he fumbles through his sack, "Would you like a pamphlet? I've made them myself."

The title of the pamphlet reads, 'Bahamut: How Can One Being Be So Cool?'

"Sorry, I usually give these ones to the youths, I have seemed to given out all my others."

Balian shrugs with the resignation of someone who didn't quite get the opportunity to engage in formal learning as a child.  "Resonators... Mabaran...big words that don't mean much at this point in time.  It was the monsters and undead that got my attention."

Noticing Shale worriedly looking for Brix, he smiles at the Genasi.  "Not to worry, he may act like an excitable but hideously deformed puppy, but fortunately I have his 'dog whistle'."  Rummaging around in one of his many pockets, Balian produces a handful of copper coins.  "Observe."

The half-elf throws the coins into the air, and they land on the floor with an unmistakable jingle.  The tunnel falls quiet, as everyone waits for some grandiose entrance, or for the goblin to simply appear from thin air.  After an awkward few seconds, Balian's face falls.

"Bugger.  I thought that would work.  It usually works.  I guess he's finally legged it with as much loot as he could carry.  Given we normally share our finds, it was possibly a bad idea letting him have everything from the sarcophagi in one go, must have gone to his head."

Eyeing the new arrivals, he continues, "Well I guess we've swapped out a goblin with anger management issues for two strapping dragonborn.  I'd say it's a good deal in anyone's coin."

The thief bows before the second equally-polite dragonborn.  "Well met Cleric, or was it Celric?  Both I suppose!"  He lets out a short laugh.  "I'll take a pamphlet, always a fan of a good work of fiction..."  He snatches one from the cleric, and turns away to flick through it.  Through his murmurings, various exclamations are heard."

"(mumbling)... Eats mountains like they are sweets!...(more mumbling)...Created the universe with a fart!...(additional, prolonged mumbling)...Has 4 heads that can sing as a barbershop quartet!"  He turns to Celric, barely-contained excitement visible on his face.  "This guy is awesome, where can I learn more?!"

The combined group begins to make their way down the as yet unexplored passageway, trudging into the shallow water, those toward the front spot some flames flickering up through the water; a most unusual sight to see a partially submerged fire. Jarl quickly notices that the fire is emanating from a robe, which is in a heap in the water.

Squiggles nods at his two new companions. "Apologies for the illusion. I err on the side of caution.  Not often I see dragon kin. What has dedicated you to this quest?  Knowledge? The Promise of riches? Silly godly altruism?"

"No worries, friend," Flynt said. "We have come to Avlor seeking the Mabaran Resonator and heard it might be somewhere underneath the city."  

Jarl fishes the flaming robe out of the water with his quarterstaff. “Looks like Brix dropped something.” He looks around for any other sign of where Brix went. Perception: 22 (Passive is 18) “And what did ‘Mabaran’ refer to again? I’m hoping you know more about this item we’re looking for, and where we should be looking.”

As you pick up the robe you hear two splashes, as a small crystal sphere and a small metal disc fall back into the water, having been tucked into a pocket of the robe. Reaching in the other pocket you find a crumpled hat with moons and stars on it.

There don't seem to be any signs of Brix, though with the floor covered in water, you probably wouldn't see footprints anyway.