Swamped

It's... an egg sac. Filled with tons of tiny little eggs. You've got no idea what laid it, though. It's not murderfly eggs, they're much too small and the wrong color, but who's to say it's not just as dangerous?

It's very unlikely that this could explain the shaking, though. On the other hand, the little piece of metal next to it might be a clue. It looks too smooth and even to be a chipped fragment; it's like part of a machine.

You've never heard of a machine that can shake a fortress before, but you can't say it's impossible either.

Fortunately, you always carry a sturdy jar on you. With the places you scurry around, sometimes you find weird liquid or odd bugs and it's handy to be able to bring a sample rather than have to describe it. You put the egg sac in there, so as not to crush it or lose any eggs in undesirable places, then you head back to the others.

"Don't suppose either of you know what might have laid this?" you say. Quill just shakes his head. Ringer rings their bell twice for a no, then makes a slightly different tone.

"You've got an idea, Ringer?"

Ringer makes the motions of opening and closing a cell door.

"Oh yeah. Think I heard one of the prisoners was an animal expert. Well, seeing as Shrike's recovering from desert fever, I guess that's the best person to ask." You pause. "But it's been a while since I checked in at the stupid meeting, maybe I ought to report in with what I've got first."

Ringer rings their bell a little excitedly.

"You want to ask the prisoner? Well, as long as Quill goes along to better explain things, that might work. Then again, the council might want to see the eggs for themselves. I'll need to think about this for a moment."