Between Vanizi, Davis, and Katarina, you kill the blue mage and drop the pink one to their knees, not dead but clearly out of the fight. (You can take one cultist and one mage prisoner if you wish.) These two mages each wear a necklace of human teeth and carry a set of keys that look like they would fit the padlocks of the cells you saw before. Between the cultists, you find various coins and a cheap jewelry that amount to 100gp. (Updated map)

In the room that you are in, tables and chairs are arranged to create a meeting room or mess hall. Water drips from a pipe into a basin in the southeast corner beneath a detailed image of a staring eye gripped in a withered hand. There are closed doors in the north and south walls, and an open door in the west wall where the two mages came from. In that next room (C16), bones in nooks along this wall were pushed aside to make room for folded robes and other personal effects. Four narrow cots lie against the north wall. 

"AAAAAAAAAHHHHHHH!!!!!!!.........oh, are we done?" Zyl sighs and relaxes, returning to her normal fun size and stows her axe. "Well nothing but storage in there, but what's with the whole creepy eye thing. OHHH this is like that thing we saw that one time in the other thing with the...okay. Well, should we try these other doors here?" She'll flutter over to the north door and try to open it.

The door in the north wall opens easily enough, showing a 5' wide passage leading north and then down a long staircase to a T intersection with a passage running east to west. (Map)

Davis will take some rope and tie up the mage and cultist, careful to make sure the mage can't cast any spells. He will then take the necklaces of teeth, giving both of them condescending looks of disappointment.

He then takes the coins and jewelry, "These will be donated to the Church of Lathander, or Tyr, possibly Selune, well Moradin, Garl Glittergold, and Torm are also good choices." [Davis will continue to name goodly deities, for a minute or two, looking to anger, frustrate, or just annoy them.]

He will take their keys and hand them to Vanizi. 

Looking back at the cultists he'll continue "We have already rescued two of your prisoners, and as you can tell, we will soon rescue the rest. Tell us where the other two are, and about how the pipes work, in the spirit of cooperation, and I won't ask my friend here," he nods at zyl, "to burn you to a pile of ash. OK, who is first..."

He pulls out his coin, "heads" he says, looking at the cultist, "tails," looking at the mage. He flips and catches it, revealing the coin, "looks like it's you" he says, looking at the cultist. "Tell me what you know now, or, burn."

If you want a roll... Intimidation 29 (nat 20) [I used a luck point to roll twice]

(Nice! The module says they fight to the death, but I will always reward great role-playing and a great roll!!)

The mage says to the cultist, "Memory of Vecna, still your tongue, or have it ripped out and fed to you!"  

The cultist glances nervously at the mage, who is scowling at him, then at Zyllynne, who is giving her best fairy-sized scowl right back. He seems undecided on which path lies the least amount of pain. Finally, after a last look at the mage, he says, "The prisoners are in cells through that door." He nods his head to the north door. "I don't know about the water pipes, other than an elemental gets surly with us if we go into the valve room." He looks at the mage again before ducking his head and staring at the floor, barely keeping conscious.

Davis will put the coins and jewelry in a pouch to deal with later. 

He will grasp the the cultist by the chin, "You did the right thing, perhaps for the first time in a long time" and he will let a bit of Tymora's magic flow from his fingers and heal the cultist for 1 HP. [Lay on Hands] 

Davis looks at the others, "Lets leave them here for now, we have two prisoners to find. Did anyone search their bodies for anything useful? The mages came from the west if we want to search that room before continuing north."

Davis will head to the north door that Zyl opened, and wait, in case anyone wants to search the rooms, when that is done, he will continue down the stairs, stoically.

Vanizi takes the keys as Davis hands them to her. then stands near at hand as he questions the two captives. She listens carefully, trying to tell if cultist might be trying to deceive them, especially after the mage's words. (Insight: 18)

Cultist roll: 13

The cultist seems to be telling the truth.

“Wow Davis, you’re on speaking terms with all of those gods?!” Celeste thinks out loud in gentle awe. She then moves to trying to make herself bigger by puffing her chest and correcting her posture to stand at full height to support the paladin and the fairy in their intimidation, even though they were clearly pros!

”Oh hey! We met that elemental. I wanted to call them Flow.” The druid notes at the mention of them and the pipes.

”We’re not going to… sniff sniff… let them go free… huff huff… right? We should probably… sniff sniff… turn them in to the authorities at least, yeah? Of course, sniiiffffff… after we save the other prisoners… sniff sniff sniff.” Celeste chatters along after Davis, nipping at his heels and naturally, was sniffing and huffing along. She’d do all the sniff checks, snooping and sifting through the new spaces. The druid keeps her nose, eyes and ears alert for any traps, secret passages, and hints of other living, or undead, beings. 

Perception Passive: 19

Katarina can't help but scowl at the two cultists...

"Katarina thinks it would be best to silence them, before they can cast any spells," she points out. "Katarina wouldn't want these jerks to come up behind her while fighting something meaner than them..."

(Katarina is ready to move on as soon as the cultists are thoroughly secured)

Perception: 11 (passive 16)

Map

Moving further down into the crypts, you come to a T passage. To the right (E) the passage goes 20' before opening into a larger room (yellow callout #6). There is a door on the north side of the passage about halfway between where you are and the larger room (yellow callout #5). Looking left (W), you see a series of doors on either side (yellow callouts # 4(N) and #3(S), and the passage eventually appears to turn left (Yellow callout #2(S)) at another door (yellow callout #1).

DC18 perception

 DC21 perception:

(Vanizi Perception: 26) 

"Movement to the east," she says in a very soft voice. "If we're cautious they may not notice us. We should check there first." 

Davis nods, and whispers "I heard something too, let's go look before we start opening these doors and are force to fight in this hallway."

Davis will sneak up to the end of the hallway to the east, ready to enter the room and engage if he see's cultists.

17 w/disadvantage

(If the party is moving to the east, everyone make a Stealth check - we'll do a Group check =)

Kat stealth: 14

(Hahaha Natural 1 baby let's goooooooooooo!)

(Vanizi Stealth: 1 also) 

Davis walks carefully, slowly, focused, knowing the armor plates that cover him make a lot of noise. But he is careful, and he is quiet. Behind him though, ...

(Rofl that is epic)

The group tries to quietly approach the open room to the east where they heard activity, but a couple of you find the uneven flooring, broken by a deep root, and stumble into each other! Luckily, Davis was just peeking into the chamber to see a large (40'x20') room with long, low shelves along each wall. They are canted at irregular angles due to the uneven stones in the floor, yet still crammed with books, scrolls, and folios. Four robed cultists stand near the eastern shelves instructing two ghouls to tidy up the books. Apparently, they each have different ideas on how to organize them - as you were approaching you could hear them giving conflicting directions to their 'workers' - the ghouls. However, when Zyl and Vanizi trip and knock into each other, all of the cultists and ghouls stop and turn towards the passage, spotting your party. (Map)

Roll initiative!!
Cultists: 5
Ghouls: 17