Twig examines the symbol on the skull but doesn't have a clue what it could mean. She sees nothing out of place in the hallway.

 What's the worst that can happen?

Garth walked in the room, picked up the skull, and stood waiting to see if anything happened.

Garth picked up the skull and stood in the hallway. Nothing happened. 

Twigs eyebrows raise in surprise “I expected something to happen....but this may be preferable.”

Twig verifies that the room under the stairs is in fact, empty, and moves on to the next closest door.

”Alright, onto another door I guess,” She says, opening that door. 

Twig opens the door opposite the stairs and is greeted by what appears to be a sitting room. It’s square, about 15 feet on each wall, with a comfortable-looking sofa and chairs. The quality material and engraved wood mark these items of furniture to be of high quality. On a coffee table in the middle of the room is a glass decanter of glowing violet liquid.

Twig looks to her companions “I’m not touching that. Not until after I’ve seen more, at least...” she moves to the next door on the same side of the hall, working in an uncharacteristically orderly fashion. 

Looking excitedly to her companions, she opens the door. 

Rivana nods in agreement at Twig's caution and follows the Tabaxi to the next door. 

Twig opens the first door on the left down the hallway and sees a long, finely crafted dining table that dominates the center of the room. Sitting in each of the eight chairs around the table are skeletal remains dressed in fine attire. Shockingly, the head of each dinner guest is missing. Set out in front of each skeleton is a large plate with a metal cloche. The table is also adorned with fine cutlery and two silver candelabras. On the South wall is a large painting of the full moon. On the North wall, there is a door leading to another room.

Unable to contain her curiosity, Twig cautiously creeps over to the table, and gingerly lifts the metal dome off of one of the plates. 

Twig lifts up the closest cloche, taking a peek under it, and sees an empty plate. 

Less cautious this time, Twig moves counterclockwise to the next headless dining guest, and removes that cloche. 

(If empty, repeat until I’ve checked under all) 

Upon lifting the second cloche, Twig finds a skull with another symbol etched into it. 

After going through all of the other cloches, she finds them empty. 

(This is the place where the skull is. Middle seat on the near side of the table. 3 seats on each side, with 1 seat on the table ends.You entered into a door on the East wall. The skull is on the East side of the table.)

"Hmm, I wonder if we're supposed to put the skulls back on the necks they belong to." Garth said after noticing the symbol on the new skull.

He began walking around the table, examining each skeleton and their clothing, looking for the two symbols they found on the skulls or any useful clues.

Perception: 15

Garth doesn't notice anything in particular about the skeletons or their clothing, other than that they look well-dressed. The silverware also looks pretty expensive.

Rivana, getting a good look at the skulls, chimes in "Hey!" and then looks at the painting of the full moon and then back at the skulls, "I think these symbols are the phases of the moon! This one looks like... Yeah! The third-quarter moon. That other one you're holding is... waxing crescent? I think? It's been a while." 

Twig looks at the painting of the full moon on the wall.

“And we know just how to place them, if we can find the rest,” she grins. 

“Lets see if we can find some more!” Twig hurries out of the room, on to the next room in the hall.

(I am assuming that you guys are tagging along, if not,  say so and we’ll back-edit)

When she gets to the door, she opens it with excitement and caution. 

Twig leaves the room and heads back to the main hallway, opening the door opposite the room she was just in. (The one adjacent to the stairs)

The room is square, about twenty feet across, and has comfortable chairs and other fine furnishings. In the corner of the room is a large ornate vase. Up against the south wall is a matching pair of wooden chairs and a solid block table with a marble surface marked into black and white squares. Pieces have been laid out on the squares for a game of Dragon Chess, a popular game played amongst nobility. It appears as if someone left a game unfinished. Based on the turn counter, it shows that it is now black’s turn.

Garth walked into the room and immediately headed to the large vase to peer inside.  After looking inside (assuming that he tells the group if he found anything) he then walked over the game board and examined the pieces.

"I remember seeing a few nobles play this in my campaigning days.  Those crazy bastards would sometimes be playing while men literally fought and died a few miles away from them.  It's a shame that any nobles I happened across while playing always seemed to 'develop' dysentery."  He said with a wistful expression on his face.  After a few moments of studying the board, he moved the black knight from C2 to E3, and shouted, "Check!"

As Garth moves the knight from E2 to C3(I'm guessing that's what you meant) there is an audible CLICK sound and a hidden compartment in the base of the table opens up to reveal another skull. 

Rivana takes a look at the board. "Well done, big guy. I wouldn't have pegged you for a chess-type. Hmm... that looks like the... Waxing Gibbous? I'm pretty sure that's the Waxing Gibbous symbol on this skull."

Twig claps excitedly at Garth’s tabletop triumph.  Grinning at Garth and Rivana, she leaves the skull for one of them to carry, and moves to the next room, opening the door with as much caution as her enthusiasm allows.

Twig opens the second door on the right down the hallway and sees a rectangular room, about 25 feet by 20 feet. It’s filled with two ornate divans, several chairs, and a few tables. The walls of the room are entirely covered with mounted butterflies of all shapes, sizes, and colors. Sitting on one of the tables is a jar which contains what appear to be three live butterflies. At the bottom of the jar is a golden yellow gemstone that appears to be extremely valuable. (Like, 1000gp valuable)

"I'm starting to sense a pattern with these rooms. Seems we should expect to find a skull in each of them. So far we've got to rooms that Twig opened the door to and we have not explored." Garth said.

Walking up to Twig, he put his hand on her shoulder before she could enter the creepy butterfly room. "Do you want to keep opening doors, or should we explore this room and the other room with the weird liquid on the coffee table?"