Like with the Ko'kok, we wanted to expand on the animals that inhabited the Deva's homeworld. The Nav'raal are what the Deva use instead of horses. Either as powerful beasts of burden or as war war steeds, the Deva ride these huge feathered serpents bare back, controlling them only with their thighs. One of these will show up momentarily at the beginning of next chapter and I hope we'll have more opportunities to see them in other scenes in the future.