The NE doorway opens up into a large two-tiered room with a staircase to the North, and a large brazier on the second level to the East. The second level is 10' up, and the ceiling is 20' high. The NW portion of the room is not visible from the doorway, though it is clear that the room continues that way.
Nobody's passive perception/investigation gleans any traps.
Once you get about 10' into the room to look to the NW section, two ethereal figures pass through the North wall and float above the ground of the second level. They are dressed in unrecognizable garb, probably from an era centuries ago when this place was still in use, and each carrying a barely corporeal longsword. A disembodied voice echoes, "An offering of worth for access to the vault." Both figures point their swords at the brazier and stare at you, unblinking, their long hair and cloaks waving in a breeze that doesn't exist.
There is a door that still stands in the doorway to the NW. It looks sturdy, despite the years and all the other doors in this place rotting away.
I shrug, not that anyone could tell. Welp, I dunno guys. I'll let someone else figure this out.. I'll stay with whoever takes point. 4 history check on those guys and maybe what might make a worthy offering. Share my thoughts with the group.
Dustfinger carefully approaches the brazier, removing two items from his satchel. "I give you a trophy of my greatest glory," he says, placing Venomfang's scale into the brazier, "and a token of my deepest regret." Dustfinger rests his glass chess piece next to the scale.
There is no response from the ghostly personas at Az Emberi's question. However, at the moment something is placed in the brazier, the voice echoes again. "Now, set the offering ablaze to light the way."
"That scale was really the most important thing to me. You know, because, uh... anyway, uh... this chess piece really just doesn't belong here. Alongside the great worthiness that is the scale. You know... Yeah. That." Dustfinger lifts the chess piece well above the brazier, half flinching.
Dusty smiles appreciatively, and gives the chess piece a little toss and catches it one handed. "Fantastic. Super. It was great doing business with you, uh, corporeally challenged folk. You've been super helpful!" Dustfinger whistles as he struts over to the vault door to unlock it.