Nothing of interest on the cult fanatic. He was part of the entrance guards, but decided to hang out in a different room than the others.
(Maybe he didn't like the smell, of the floating monster brains or the gambling villagers.)

The previous room/hall had finished stonework. Walls and archways were flat with relatively sharp corners and edges. This room (and the passage leading to the hole in the wall) is very rough and uneven. It hasn't been worked on recently, but more stone work will be needed before it stops looking like a cave.

(The likely choices of what to do next are: go down the stairs to the unlit level below, go back to the entrance hall with the locked western door, or the entrance hall southern unlocked double doors.)

Jorin look sheepishly at Drusk, "Perhaps you are correct.  I do let my temper get the better of me quite often.  I will try to...show some restraint.  I do think we should continue exploring this dark passage, I could not see very far down it."

Quillary peers into the dark hole and shrugs. "Very well." She will heft her shield and proceed down the tunnel (with her dark vision).

Hildigrim is disappointed in not finding anything of worth, but not entirely surprised. At the mention of darkness, he brings one of his glowing orbs into being and has it hover just above the floor in front of him. Feeling a little more confident about putting one foot in front of the other, he follows Quillary down the stairs.

(I'll post a map when the group is a little further into the lower level.
Quillary's Pass Without Trace will expire after the next room encountered.)

Drusk suggests putting a cloak in front of Hildigrim's glowing orb.
A light will still stand out in this darkness, but perhaps it will be a little less obvious.

At the bottom of the stairs, the passage continues 10' west, then forms a T-intersection going north and south.
The north passage gradually curves a bit to the west, so your view is blocked after 15'.
The south passage curves to the west after 5', then forms another T-intersection, continuing west and also going south.

Jorin peers into the murkey darkness and says, "Catacombs may be?" and turns to the take the first passage north.

(OOC: The information given only required Arcana proficiency or a successful check. However, it makes sense in the story for Hildigrim to get that knowledge in the way described. If you are ever curious if a character had to do something in a specific way, or if I am embellishing the events to match a check roll, don't hesitate to ask.)

Following Jorin's lead, the party move north. The passage curves west then back north, and after 20' you arrive in a 40' x 20' room. The stonework is still rough, but the room walls are almost completed. The floor has been finished and is smooth.

As you look around the floor, Jorin's guess about catacombs was surprisingly close to what you see. This dark, dead-end chamber holds a mound of charred bones, desiccated body parts, and skulls scattered across a linen sheet. Strange red-black runes mark the sheet’s edges, seemingly scribed in blood.

Hildigrim recalls the the research he did concerning the Retribution of the Ancients, the tome with monstrous cover art that Sarah sketched in her diary.
The second hand information about the tome mentioned that Gaernoo would ask its cultists to pile up those ritually slain. Hildigrim interprets the runes on the sheet to realize that these remains are being collected to fuel a huge ritual at a later date—one that will ultimately require hundreds of victims. (Quillary's knowledge of medicine and her unique background has her determine that there a dozen victims here.)

The party makes a cursory search for any identification or unusual items, but do not see anything.
Drusk says a short prayer for the victims, and will make arrangements for the bodies later, after the cultists are stopped.

(OOC: The usual D&D character action is to dig though the bodies to make sure there isn't anything hidden, but in "reality" that would be gruesome and disturbing. There is nothing more to find here.)

Quillary’s face gets dark, her eyes hard, as she takes in the scene. “Not many, just a dozen,” she offers as the group consider what they are seeing, but her voice is flat. 

(OOC > can her spores do necrotic damage to the blood on the sheet to deface or erase it? If so, this is what she will do. If not, she will try, but then try to light the linen sheet on fire with her Druidcraft.)

Quote from Mingofaust >>

Quillary’s face gets dark, her eyes hard, as she takes in the scene. “Not many, just a dozen,” she offers as the group consider what they are seeing, but her voice is flat. 

(OOC > can her spores do necrotic damage to the blood on the sheet to deface or erase it? If so, this is what she will do. If not, she will try, but then try to light the linen sheet on fire with her Druidcraft.)

Quillary keeps her voice flat, but the swirling spores become more frantic.
They swirl over the edges of the sheet, and the runes are scorched until they are no longer recognizable.

Jorin watches Quillary erase the runes and spits, "We were, once again, of a mind."  He turns to head back out of the room, "We will kill them all."

Once everyone follows, he will lead the group to the left, taking the passage that goes due west at the intersection.

Hildi makes a small noise in the back of his throat, and in his eyes appears slight disappointment. But after watching the spores, he sighs and nods ascent to Quillary's defacement of the runes. "It's clear the deaths of his family has done nothing to slow him down," the halfling finally says. "These must be the remains of the missing travelers we heard about earlier." He looks up at Jorin. "Where to next?"

The spell Pass Without Trace has worn off, but (at least for the moment) the recent sights have the party impatient and pressing forward with less caution.

Join leads the group back to the passageway, and heads west. It goes west 15', turns north for another 15', then curves northwest for 15'. Your way forward is then closed off by locked iron-bar doors. Beyond is a cave, roughly 10' across. You don't see anything inside the cell.

(If you wanted to go inside for some reason, it will require a DC 15 Thieves' Tool (DEX) check to open the door. You would have an extra d4 from Drusk's Guidance.
Or you can turn around and try that southern passage.)

(Can we see the back of the cell/cave? Or is there possibly someone (or something) hidden within the cell?)

(There are no hidden corners or hiding spots, so you are confident there are no Small or Medium objects in the cell.
However, the view from 15-20 ft. away through the bars, limits your investigation.)

Drusk: "If this cult is capturing people, does this empty cell mean they have run out of captives? Or is there a reason why this cell is empty?"

 Jorin would like to aggressively sniff the area around the cage, wondering if there might be an invisible, yet smelly, creature inside.

Perception (Smell): 13

Jorin can smell blood, sweat, and urine... which isn't too unusual for a jail cell.
Nothing "fresh".

(If you are worried about something invisible, you could wait 10 minutes for Hildigrim to cast Detect Magic as a ritual.
But I'd count that time against the party, for some cultist to notice the guards are gone or slaughtered.)

Quillary bangs her cudgel lightly between the bars, not loud enough to be heard at a distance, but enough for anything within to be sure they are not alone.

When (if) nothing comes of it, she turns and moves to try the next passage. 

Quillary doesn't notice anything.

(I'll wait to hear if Hildigrim wants to do anything.)

Volo nibbles on Hildi's ear, and after a half-hearted wave of his hand at the bothersome owl, the halfling smacks his forehead. "Yes, of course. Please, go take a look." Volo flies in, and Hildi closes his eyes to peer through the eyes of the familiar.

Volo's perception with advantage on Wisdom (Perception) checks that rely on hearing or sight: 15

Volo slips past the cell bars and flies around the cell.

When the owl prompts Hildigrim, he spends a few moments using the owl's senses.

Volo notices a 5' spot on the floor that is more worn down than the rest, and has more blood, sweat, and urine than the rest of the floor. It has taken some impacts.
The owl then flies straight up from that spot. There is a 5' square patch of the ceiling that isn't quite even with the rest of the ceiling. One side of that square has hinges.