Its all in the Cards.

Tempted as he was to allow the ghost children to take the lead and destroy themselves, Ashtar stepped ahead and took the lead. Gripping his quarterstaff by his side, he moved forward and left.

With a torch now lit the party moves a bit easier in these muddy tunnels.
A muffled mumbled sound of indistinguishable indescribable ritualistic chanting starts up and echoes throughout the tunnels.

The torch light shows the tunnel to the right has two large stone slabs imbedded in the wall. One of them has something etched into it but you need to get a bit closer to make it out.

The tunnel continues to the left and goes down a slap stone set of stairs.
At the bottom of the stairs you see a table with a few chairs around it.

Ashtar descends down the stairs slowly, eyes darting about to take in his surroundings.

"Oh this is wonderful," whispers the fairy. "Great, just great." Nervously licking her lips, she unfastens the clips holding her hand crossbows in place, making them easier to draw if the need arises. She catches glimpse of the mysterious slabs to the right and a hint of a workspace to the left. She nudges Ashtar with an elbow and speaks low, "Think the desk first? Maybe find some clues?"

Down the damp mud and stone stairs the party finds, a weathered wooden table and four chairs huddle together. A leather bound book sits on top of the table.
Across the chilling expanse, four alcoves loom menacingly, their depths shrouded in darkness and harboring nothing but moldy straw pallets that emit a faint, musty scent reminiscent of forgotten souls and lost dreams.

A tunnel leads on to the left...

Ashtar heads past the table, and pauses to give everyone time and space to gather. He checks the table to see if anything about it is amiss, and inspects each alcove, before heading back and checking to see if everyone was ready to move forward.

Alyria, who followed behind Briar, wanders over to read the writings on the wall. A part of her mind that remains her is wondering how well she'll process words since she's seeing through the eyes of a six-year-old, but decides that it should all be fine in the end. At least as long as she never has to feel this constantly afraid again.

On the table is a leather Log Book. The book's pages are filled with entries of what appears to be unwilling sacrifices of some sort. The book has over a dozen pages and each page has about 20 entries.
The last page is as follows.

While her companions look for details among the items in the space, Briar remains on alert. She pulls her hooded lantern out again and keeps her eyes roaming about their surroundings in hopes of catching any unexpected movement during the pause in their progress.

Ashtar shuddered at the entries in the log book. Whoever was doing this really ought to be put down.

"It's this way!" Eye of the Storm said with pride as he pointed southwards. He knew stuff!

"Oh!" Briar yelps as Eye of the Storm indicates the next path. She looks to Ashtar. "Onward then?" She creeps forward in the direction indicated, scanning around as they move into the newer area.

The party does an about face as Rose of the Storm squeezes pass and changes direction.
Leading everyone back to where they started the party passes once again two stone slaps that stuck into the wall.
One Slap has a plaque with writing etched into it. (White Dot)
Following the tunnel down to a tunnel that splits to the Left and Right then continues straight forward.
To the left you see two more heavy Stone Slaps (Red and Green Dots) with plaques. Each plaque has something etched into it but it has to make out in this light.
To the right are two more heavy Stone Slaps (Yellow & Pink Dots) with plaque with words etched into it. It is once again hard to make out what it says.
The torch's light reveals the tunnel forward has a table of some sort.

Ashtar caught Briar’s eyes, but kept a straight face. If the kid wanted to take the lead, it’s just swell with him. One place was as good as another.

The fairy looks to the tabaxi and tentatively inquires, "Rose, do you know what those big stones are all about? Or what that room ahead is?" If the children want to come along, they may as well share any knowledge they have, she figures.