|Image by Greg Staples: http://www.gregstaples.co.uk/|
The angels were created each according to its function; an angel IS its name, its function. It has no real existence outside of that. Angels are not really possessed of free will in any meaningful sense. They cannot act against their nature. At root, angels are messengers; they carry the messages of the divine will to creation. They are, in a very real sense, action without volition, light without fire.
Before long, God realized that the angels were not good companions for him. They were not like him, they could not imagine, could not create. They were not possessed of the divine spark in whose heat nothing is forged into something. And so he created the djinn from flame without smoke. This too is a radical idea. While we are accustomed to the clean-burning flames of gas and alcohol fires, this was not the case in times gone by. Imagine that the only fire you've seen is a dirty, smokey, sooty thing that burns your eyes and stings your throat. Now, imagine a fire WITHOUT smoke; pure flame, pure passion, pure will, uncomplicated by matter. That's what the djinn are made of.
So, now that I've told my little story, here are some details about them from myth and lore. Djinn are a kind of non-human, sentient creature very similar (or possible identical to) faeries. They have individual personalities and names. Like faeries, they are violently allergic to iron. They are not, strictly, immortal in the same way that angels are, but they don't really age and they are hard to kill. They are possessed of free will the same way humans are. Again, like faeries, they eat and drink, and can interbreed with humans. They live in wild places, and in ruins. They fall into three basic "courts": some are pro-human, and generally helpful and beneficent. Some hate humans, and are eager to fuck you over at every turn. Some don't really care much, one way or the other, and mostly avoid getting involved with human affairs.