Halhace will go through the door and look around curiously, his hand keeping a tight grip of his staff. "Before we touch anything we should check for traps and the like."

Investigation: 4

(Taking it, as we all are I'm assuming).

Dhara would follow in behind Halhace and since he clearly found no  traps would look through the room both for anything valuable or interesting but also for any indication as to what it was or who occupied it previously.

Investigation: 6

(no, I mean the embellished locked box, sorry!)

Jaylen suggests to the group "Let's move slowly, no knowing what manner of traps my have been left"

Jayne listens intently at the now open door trying to pick out any unusual sounds Perception: 12

If it is relevant passive perception is 15

Halhace, you don’t see any traps in your vicinity.

Jaylen stops at the door and quietly listens for a moment. It is very quiet.

Dhara ventures further into the room. The cupboards seem to hold different vials, some empty or broken, but others still holding liquids. You also see different skeletons of smaller creatures, scales, feathers and other items that might be used in potion making or other alchemic ventures. Everything is covered in layer of dust.
By the back wall, furthest away from the doors, you find a stone bed covered with what used to be a mattress made of cloth and straw, long decayed. Next to it along the wall are three wooden chests. Two of them have a normal lock. On the last one, where the lock should be, is an indentation of a flat circle with a skull, writing pen and a scroll in the middle.

Meep follows the others into the room, staying close to Dhara as he peered about. None too happy about leaving the tunnels that were his comfort zone. Walking past a few skeletons, the kobold would pocket and store what he could. The chests meaning nothing to him. 

Dhara takes the small box and attempts to open it with as little damage as possible.

Strength: 7

Dhara manages to force the embellished box open, but she somewhat damages the hinges. Inside she finds a leather-bound diary, a note and two medallions – palm sized coins made of different metals, one with a tint of brown, and the other of gold. Both medallions have a skull, writing pen (quill) and scroll engraved in the middle.

(We don't have a lock picker amongst us 🤔)

(Yeah I am not sure if we have a rogue....)

Kamos followed the group into the room.

Perception: 6

Kamos is just looking around the room, not looking for anything in particular.

(yeah no rogues amongst us.)

Halhace looks around but sneezes mid search but is satisfied that he did not see anything he would have reason to consider a trap. "Seems safe enough...."

What color is the indentation on the chest?

(You can always break locked stuff or find the key, right?)

Kamos follows after Dhara, looking around. In one of the cupboards you notice a quarterstaff with a small carving of wings on the top of it. As you reach the back wall you notice a metallic shimmer amongst the cloth and straw that used to be a bed. Taking a closer look, you find a simple metal key.

(Dhara; Its brown, as it’s made of wood.)

Kamos: (to the party) "I think I found a key to your chest. I also found this wooden stick."

”I think we should check for magical traps and items”

Jayden Ritual casts detect magic

"Well unless it it better then the one that I already have you can keep that staff." Halhace says as he steps forward with the one he had been with since they had fled the arena.

Ok, pending Jayden's results I'll also check for non-magical traps and assuming there are none, try to use the key of the same color to open the chest.

Meep, as you are following after Dhara and picking up random things, you managed to get 3 scales, a deep green stone, 5 bone shards, 2 chalk (1 piece) and 5 silver coins.

In the ten minutes it takes Jaylen to prepare detect magic, Dhara looks for traps and does not find any.

Jaylen, now with detect magic active, you see the quarterstaff Kamos mentioned is emitting a magic aura. You also see an aura coming from one of the wooden chests with a normal lock.

Dhara, the medallion fits perfectly into the slot on the chest. As you push it in place you hear a loud click and the chest opens up. Inside is a single glass globe which seems to hold brown rock formations in the middle. You notice there are letters carved into the glass, but you can’t read them.
(Dhara, roll perception please)

Meep doesn't tell the others about the treasures he's collecting, but he's not making any attempt to hide it either. When Dhara opens the chest, Meep will drop his head inside,  assuming he's tall enough. Otherwise, he'll put his nose over it.