Realizing the danger, Gunra will relay Harmony's message in draconic.

Nurm, you guess that the egg could belong to another race than the other two. Maybe a white dragon?

The drakes stare at the group for a long moment, one of them cocks its head as if not understanding, but they obey the order for now and go sit at the corner Harmony pointed at them.

Petmailer walks down into the chamber.  Perception :  4

"I think that we should dispose of the black eggs and keep the silver egg.   What do you think, how should we do it?"

Gunra, satisfied that the drakes were not an immediate threat, joins the others at the eggs.  His capable friends had spotted a third egg, and he was feeling further conflicted.

"Well, taking the axe to the egg would probably do it.  Or we could throw them to that automaton.  It would do the work for us."

((Granted, Gunra's experience with dragons isn't exhaustive, but is he able to identify the pale dragon egg?))

Gunra, while you can tell that the dark eggs are of Black dragons, the gray one is harder to guess: Given how it was located closer to the cold of the stalactites, you know it is either a Silver or a White, but you can't tell which one. It wouldn't make much sense for a cult of Tiamat to keep a metallic dragon egg around, though...

The eggshells seem strong, but they can be cracked with the strike of a weapon.

Still sitting on the corner, the drakes don't react while you inspect the gray egg, but seem to grow agitated when the black ones are threatened: If the eggs are destroyed in front of the drakes, they might attack.

To investigate the eggs further, roll for Arcana or Nature. You can choose which to roll for, or make two rolls for both.

Arcana 18

Nature 6

Arcana: 18

Gunra, after inspecting the eggs and comparing them to what you know about the nature of dragons, you find two bizarre discoveries: 

The first one is that the pale gray one is definitely a silver dragon's egg, a metallic dragon known to be both powerful and benevolent, so how and why this egg would be on the cult's possession and why would they guard it here along with two chromatic eggs is confusing.

The second one both answers this and confuses the situation even more: Both the silver egg and the two black eggs have the same scaled texture, which to your knowledge must mean that all three must have been laid by the same mother. The silver egg also has the same 'age' as the other two.

If all three eggs were both chromatic in nature, this wouldn't be weird at all: When two different colored dragons mate, the offspring will always belong to one color or the other, with litters sometimes having siblings of both races. The same thing happens with metallic dragons: A silver/brass couple will have children that are either silver or brass, and viceversa. But Chromatic/Metallic couples are completely unheard of, not to mention being thought to be impossible. 

And yet... Here we have one silver egg and two black eggs from what appears to have been the same parents. Why and how, you can only theorize, as there's no many other clues left here aside from the three eggs and the two blue drakes guarding them.

This egg being that of a metallic dragon does answer some questions, though: Why this one was among the stones while the two had better nests, for example. It could also explain why the cult didn't put better security here: Maybe they didn't bother to protect these eggs better because they believe their metallic lineage "taints" them somehow, but that doesn't keep them from wanting to raise them as soldiers.

"Hmmmph," grunts Gunra as he sizes up the eggs.  He was visibly vexxed. "Good eye, Nurm.  But I got'a new problem now."

"One silver, two black.  All from the same parents.  Not supposed ta happen, but gnolls aren't supposed to be good puppies either.  Definitely want to save the silver from bad parenting.  But if we smash the black eggs, those drakes are definitely gonna come at us. . . and it will be years, decades at least before those two black eggs grow into anything like what we saw at Greenest."

“So...definitely save the silver egg...what about the black ones? I’ve studied Draconia most of my life...but I never thought I would encounter this situation.” Kane stays away from the eggs, as to not upset the drakes. 

Hmm, If we leave the eggs to the cult, nothing good will come of it, it may take some time but they will cause trouble in the future. Unless we find a way to carry all of them out, I think we should destroy them. Even when it means fighting the drakes.

Petmailer says “I think we should take the silver egg and leave the other two alone.  I do not want to tangle with those drakes.  What I can’t figure out is how we will get it out of here.”  He pauses to make a show for the drakes that he is cleaning, caring for the eggs, polishing them, using prestidigitation as needed to dirty, then clean, etc.  “Has anyone seen a cart anywhere, or have an ability to create a minor illusion over the egg to disguise it as we roll it out?”

Petmailer walks over and picks up the silver egg, still continuing his polishing routine, looks out of the corner of his eye for any reaction from the drakes.

"Draconia?" The name of the place distracts Gunra momentarily. "I have never heard of such a place in the Realms.  Perhaps you can tell me about it some day."

Seemingly remembering the urgency of their task, the tortle glances back to the guard drakes, puffs up his chest, and tries to take a page from Harmony's book.  As he speaks, unwittingly, he does so in Draconic - a language he was recently given mastery of.

"Softskin leader wants to move the pale egg.  She says we need you to guard the black eggs.  They are important.  We guard the pale egg."

Gunra carefully puts away his shield and extinguishes his torch before carefully reaching towards the pale egg.

Gunra, the drakes seem to understand your words and drop their guard, no longer looking at you. They walk closer to the black eggs' nests and lay there.

((Didn't Nurm suggested a spell he could put in the egg to make it weight less, or something? If not, then I can rule out that Gunra can carry it on his backpack because his backpack happens to be big enough. Because tortle.))

If Gunra's backpack is large enough, Petmailer suggests that we put it inside and then cover all with the cultist robes (out of sight of the drakes), making Gunra a Humpback Tortle.  

Kane looks at Gunra. “Oh, it’s not a place. It refers to the study of dragons. Another word could be dracology, but draconia sounds better.” Kane sees that the drakes moves to the black eggs. “Alright, how are going to get this out of here?”

((Alright, Tortle of Notre Dame it is, I guess.))

You carry the silver egg and gently put it inside your bag. You sometimes hear the aforementioned sounds, but that's about it. 

As you all walk away, the two drakes stay with the black eggs you decided to spare for now.

Which direction are you taking?

Petmailer says "Let's move.  We need to keep pressing forward."  He moves to area 9 and starts to head toward the steps leading north, if that is acceptable with everyone.  After out of view of the drakes, Gunra's robe is adjusted to cover the hump of the egg in his backpack.  We are all in our cultist robes and marching forward like we are just carrying out orders.