They're magical but they don't seem to have a school of magic and she has no idea what they do.

"The trap isn't a spell, it's something stable to itself. That leaves a lot of options."

The wizard casts summon monster. 

A dog runs forward and is sliced into pieces by scythes that emerge from the walls. A fine black powder falls from the ceiling. The trap remains still after firing.

"Well. Looks like it's disarmed for now." He walks forward and jumps over the black powder. "The door is unlocked!"

She eyes the powder a little worriedly, but... manages to get over it without issue. She follows after him.

They find a room full of crates. A particularly large one has been dragged into the chamber’s center, around which stand four mismatched chairs and stools.

The captain leads them forward into the next room.

Cabinets and low benches fill this chamber. From pegs on the opposite side of the room, the empty black eyes of two beaked plague masks glare with soulless, unblinking stares.

"This room is clear of traps, as far as I can tell."

The captain nods. "Search the cabinets."

Detect Magic, of course. 

"Do Urgathoan cults use masks? And if they do, why weren't these in use? If they were planning something with disease, wouldn't get need protection already? Maybe they just all had the masks they needed."

The two plague masks have faint conjuration auras. Four flasks within a glass cabinet also have faint conjuration auras.

"I'm not sure how Urgathoan cults typically operate. The corpses in the room with the vats weren't wearing any masks."

Head tilt, some minor gestures... She looks confused. "Vats are for making things, and this is Urgathoans so it's probably a disease. I wonder why they didn't use the masks... Oh, they're magic. That might be why. Conjuration, and so are those flasks — well, probably whatever's in them." And not magical enough for Morgethai to take, or maybe she just didn't get up here.

The wizard looks over the masks under detect magic. "They mask alignment and grant immunity to a single specific disease. I don't know which one."

"Even more confusing that they weren't in use, then. Who would be coming close to the disease but isn't already?" Is she really going to have to spell out that they must be missing someone. (Maybe whoever it was who tried to murder them in the sewers? That seems likely, at least.)

Should she even do it if they can't figure it out themselves? Why does she have to ask a question like this. ...working with humans, can't forget that.

"Perhaps they wear the masks to conceal their alignment when they leave this place? Or the masks are for others who aren't here right now."

The wizard collects the masks with mage hand and moves them into a pack. He identifies the flasks as potions of cure light wounds and collects them too.

The guardsmen find some healer's kits and strange doctor's outfits but no other valuables. The captain leads them into the next room.

Black-sheeted cots fill this room; their satin coverings and overstuffed pillows seem more akin to funerary trappings than the resting places of the living. Numerous skulls are set evenly within the room’s stone walls. Candles inside them cause them to glow like morbid jack-o’-lanterns and cast dim light across the room.

"Where did they find this? That's good cloth, it can't have been cheap at this quantity. I guess we knew they had money from the magic masks."

She pauses for a moment, as of realizing something. "How long have those candles been burning? Are they actually burning? Someone must have changed them, and whoever it was probably wasn't dead then. ...probably wasn't an inanimate corpse, at least. It might have been a zombie, these are Urgathoans."

Navarro peers at one of the skulls. "They are real candles. Whatever befell the cultists must have happened recently."

The guardsmen search the room but find nothing else of interest. The numerous shelves and footlockers scattered around the room contain nothing of value.

The wizard doesn't detect any magic. The captain leads them into the next room.

Shattered panes of glass line the walls and cover the floor of this chamber. Much of the glass is melted. Heaps of dust and ash and bones are scattered across the room. Emblazoned on the ceiling is a message.

In the end may you be undead.

Any magic here?

"No corpses here, but it looks like a fight. Are those undead remains?" She nods to the heaps.

There's no magic here.