I think you have read into the Bible. I am not aware of any prohibition, Biblically, of new organism creation. I also believe there were creatures we have no idea of, unless we allow that mythology may have some base in reality.
Because the natural processes of the universe do not explain the design elements in biology. While natural selection works in micro-evolution, there is no evidence of natural selection in macro-evolution. The only plausible explanation is the designer did it.
How the designer did it, I'm not certain. I still don't buy into Biblical Genesis, but clearly something is designing organisms. In fact, I prefer to discard Genesis, because I imagine the designer is still designing new life forms on Earth. Even to this day. The Bible does not allow for that.
Dragons? We have llizards. There were lizards that flew, before they were too big survive, ice age, etc. Methane is a good enough combustion gas for the flame and most animals are pretty good at making it, and all the nights in the tales complained about the smelly breath. Need some protection for the throat mouth etc. There are plenty of animals that exist in heat extremes above and below the ocean. Some (maybe all) flamingos hunt in volcanic temperature pools for there meals. Of course it would be wiser if the flame was only outside the body. Protections could be minimal then. Now we need to ignite the flame. Maybe an electric charge? Every animal has an electrical supply, some produce obvious electircal charges; eels, fireflies. Could be done, maybe it already was.
In the past I have been challenged to imagine new organisms. As I just showed, I can imagine a pretty elaborate new organism, but science has already engineered wonderous, if itsy bitsy, organisms, such as oil spill cleaner uppers. Not in mass use yet, but we will get there.
The same can be said for aliens, as long as we are on new organisms. The Bible does not claim there is no other life or will never be other life. It is difficult reading the Bible to expect that there are other planets inhabited yet. But even in ToE there is a first inhabited planet. Maybe we are it and there more to follow. Quite possible from both views.