The game just states that many followed Arokhs example and went to sleep also. It doesn't say that all of them did. So I think its possible for their to be a small handful of Elder Breed in the world still awake.
Well, most of them perished in the Dark Wars - and of those few that survived, most (if not all) got too stoned
But more seriously - yeah, it's plausible that at least a few would have stayed behind after the Dark Wars - eg. due to having just hatched at that time, or even just after the wars' conclusion.
Alternatively, if you want to stick to the version that all
of the Elder Breed alive at that time packed up and left - it's not unlikely that some dragon eggs could have been stashed away for safekeeping (eg. protected by some powerful magic fields?) somewhere around the beginning of the Dark Wars, and then rediscovered when cleaning up the aftermath?
Rimril's place seems as good a spot for that as any - it was very well protected, since it's still standing (and mostly intact) by 600ADW, and for all that time it was under the protection of Rimril himself.
Also Rimril was part of the Order, so it only seems natural that he would agree to such a thing.
Of course after the Dark Wars, he couldn't actually leave
, so he would have to wait for someone else to show up, someone who could be trusted with these eggs...
As to why he didn't mention any of it to Rynn and Arokh when they showed up - well, that was ancient history, not relevant to the task at hand; also they hardly had any time for idle chitchat.
And Arokh, it's equally likely he wouldn't have known about it either, since he was actively participating in the Dark Wars.
For Tuiri, much the same argument applies, also she had a much bigger problem to worry about - what with being stuck as a soul shadow, and all that.
I don't believe we very get to see someone try and Bond with a Non-Elder Breed. So its not impossible just unlikely due to the bat and crow dragons being a much lower quality. I think someone very well could Bond with these lesser dragons but with possible side effects.
Hmm, but wasn't the Dragonstone a gift from the gods, granted to the Elder Breed specifically?
It would've been counterproductive to have it work for any other (lesser) "dragon" races if that were the case.
If anything, I'd be more willing to accept that a group of brilliant alchemists, mages and whatnot, analyzed the inner workings of the Dragonstone carefully, and managed to create an inferior copy that doesn't work for the Elder Breed - but does
work for the lesser races (and likely with further limitations on its effects - eg. little or no lifespan extension, and/or only temporary "Bond" duration).
EDIT: This could have very well happened well before the advent of the Dark Wars - but their creation had been shelved back then, since it didn't really work as intended, and in any case wasn't really needed at that time, since the Elder Breed was still around)
(this also opens the possibility of a darker angle, where powering the "fake Dragonstone" requires considerable amounts of human and/or dragon sacrifices - or that the process has only a very low chance of success, usually resulting in deaths of the participants instead due to some unknown, effectively random incompatibility; make of those ideas what you will)
There still remains the question of how would the "fake Dragonstone" even work in practice - since the lesser breeds we see by 600ADW, while presumably at least somewhat intelligent, also appear to be feral, aggressive and incapable of communication (at least, not with humans and the Elder Breed). Perhaps that wasn't always the case, though?
EDIT: In any case, there also needs to be some reason why there are no dragon riders (even of the lesser races) by the time of OOTF.
Perhaps the "fake Dragonstone" - which (presumably) had been crafted in the pre-Dark War times, only had a limited durability - and its complexity and/or arcane construction made it impossible to recreate in the post-war era; especially since a lot of the required knowledge would have been lost with the fall of the Order?
As stated above. Even the Dark Union is not immune to faction spiting and people seeking power.
because it's the Dark Union, which was itself formed in that way.
Also, presumably it's the reason it took them so long to restore it to at least a fraction of its former "greatness", while not being completely wiped out by the opposition.
Just remember that whatever you think up needs to be consistent with the subsequent timeline.
One way to reconcile that would be to make your story involve the demise of a promising new leader of the Dark Union, since that would have thrown a wrench in the gears; that's a good few decades of setback
As for the races I was mostly referring to Player Characters and what races they could be.
That's what I meant there. Why not goblins, too? They were obviously quite intelligent, and capable of communication (at least with the other goblins; apparently they didn't speak the human languages - or at least not by 600ADW).
EDIT: Also, moved this topic to "Dragon and fantasy discussion" subforum, where it belongs