She twirls around the metal triangle she cut out of the Mak Candelario. "Not exactly your standard keys, are they?" she quips.
Continuing, she says, "There are seven chambers around here; I'm guessing six of them have keys, the seventh being that one with the rotating floor. As for the mural, I didn't see any mural, but my party split up.
"I'm guessing you haven't seen any of them... that's not too surprising. We were very unlucky. I just lost my last two associates in the arena. Our magician turned out to be a spy, and started transforming us. Half our party lost their minds or ran off, so it was just the three of us."
After one too many yawns, Agatha replies, "Well, I don't know about you guys, but I'm going to rest now. We'll be alright from wandering monsters here, they're all too busy in there." She gestures towards the arena.
Leaning up against the wall and grasping her weapon, Agatha settles down for the night.
[I will assume the party does as well and continue with the update; if anyone wants something different, just let me know.]
When the party wakes up the next morning, Agatha is still snoring quietly. During the morning's rustlings, she snaps awake, holding her weapon aloft.
"Sorry," she apologizes a few moments later, "sleeping with a bunch of men tends to make a girl edgy, especially when you don't know if they're going to go feral and try eating you at a moment's notice."
She takes a quick peek at your map:

"I've explored a bit more than this, but I wasn't the cartographer so I don't have a map. Anyway, each of these rooms. To the west is another one of these 'key rooms', and this one called 'The Kaleidoscope' is one as well. There's a fountain to the northeast, and a few other 'rooms' to the northeast and northwest. From what I can see, the rest of this level is a twisting maze. The locked door is roughly west of here.
"I suggest we get the keys first, before we do anything else. But then my advice hasn't worked out well so far, so I'll probably just go along with whatever you guys want."
[The Archivist renews his Command over Grrarghgrllfrg]