“I'm not quite sure what you mean by reversible creatures. You mean ones that don't necessarily stay on one side, within their same type? As in, a parent could go to the Daywalkers, and a child (cousin, brother, etc.) could go to the Nightwalkers? I'd rather not have any of those at all. If you mean something else by that, though, feel free to clarify.” 

*Gathers thoughts*

Sorry this response took a while but it really took a lot of attention to work out my thoughts coherently on this one :P If you would like to have sub species inside the races that land on opposite sides of things, then it follows that there will be inter racial breeding and children that WILL have to choose one side or the other when they reach a certain age. For them, it will be a choice things. I only say this to follow true to my idea that no one thing should decide if you are a Nightwalker or a Daywalker. For many races, I see that yes, they will be most definitely on one side or the other, however with races that have sub divisions, I see a lot of “Choice” entering the matter when it comes to the more ambiguous aspects to the sides of the war. 

If you really don't want “Choice” to enter into this at all, then it would be best if we stick with singular races with no divisions, but even then, going along with what I said before, that does not eliminate the idea of choice since even in the most narrowly construed definitions of what makes someone one thing or another, there are always the exceptions. 

But I digress. When I said Riba I was talking about having sub races and inter racial children for the most part. So a dark elf and a wood elf have a kid, which side would it be on? For the most part, whichever parent that raised it would make the choice, but I have always loved a good rebellious undertone, or perhaps just freaks who just don't feel they fit in. In that respect, I had plans to have such things, but if you really are against such things, then to minimize my creativity in that respect it would be best if we went with the narrow race setting. In other words, only one race of elves, one kind of dragon(Or simply all different colors of dragons on one side, separating out the drakes, wyvrens, and flying serpents), and so on and so forth.