I thought Dragons hated humans(possibly humanoid beings) in general. If a dragon can tolerate a human it can also tolerate a demon. The question of which it will feel more threatened by could shape its reactions. Just remember the dragon riding orcs. Two questions, since dragons are demons can they not also shape shift. If they can some might pose as a humanoid demon or a mortal species as Dragons are intelligent. I don’t know how different their original species are from humans, but the concept of spies, camouflage, and scouts should be common. Dragons raise less alarm bells than demons so they could likely be more extensive throughout Astlan.
Few humans can tell one dragon apart from another dragon and they can access more places do to a lack of a need to eat, breathe, and can move freely in three dimensions. Not all dragons would be large as smaller dragons might be seen as drakes, wyrms, or wyverns. They would have a hierachy with weaker dragons as weaker species, and larger dragons being more rare. Not sure what they’ve done, but as an intelligent species they have likely formed some type of community and possibly a society that those on Astlan might not recognize.
Also the slow regenerative nature of dragons is less blatant than that of demons and might make them appear more natural as it takes time for them to recover.
Any more thoughts on dragons would be nice. I can think of more later.