Greetings fellow wiki-goers and welcome to my post. Just to inform you right away, this is going to be a lore-oriented wall of text, so if you're not interested now's the time to turn back. For those of you that are genuinely interested in the backstory of League and would like to discuss it, feel free to continue reading.
As well all know, the setting of League of Legends is the fictional world of Runeterra which is filled with a variety of different races. Now, since the introduction of Tahm Kench lore-enthusiasts have been wondering what he's supposed to be. The recent Q&A gave us a couple of answers, such as the fact that fish-boy is a river-demon and has existed since Humanity, preying on the weakness in their hearts. Naturally, connections have been made with Aatrox, another daemonic entity that resided in Runeterra and influenced its people (albeit while Tahm did so by dealing with individuals one at a time, Aatrox did so by taking command of entire armies). So this begs the question, how many daemons are really out there in Valoran?
Now, first things first, Riot stated that daemons that inhabit Runeterra are NOT like the ones we see in Christian-Judaism, even though we already have Angels and Fallen Angels. But please do note that the lore of League is a bit of a mess right now, and some Champion backgrounds are now obsolete (specifically those that mention Summoners, the Institute of War, and the Fields of Justice). This narrative chaos does leave us with more than a few questions regarding a couple of Champions, or more specifically, their origins. So one has to wonder, how many daemons of Runeterra do we already know of?
What's not a Daemon
The easiest way to figure out what is a Daemon, is by figuring out what definetly is not, a process of elimination if you will. Firstly, a daemon is (at least in a way) immortal, so members of mortal races such as Humans, Yordles, Minotaurs, Trolls, Ursine, Marai, Brackern, and Undead are disqualified. We can also rule out Voidborn, Fae, the Ascendant, Iceborn and Celestials because despite being creatures possessing immortality and otherworldly appearances (except maybe the Ascendant and Iceborn due to them being mortal men who gained their powers through ritual), they don't fit the criteria of "daemon", since they lack malicious intent ( Xerath might be an exception due to the manner in which he gained his Ascension). We can also rule out beings whose origins we know of, such as Robots, Treants, Werewolves, Cyborgs, Sentient Animals, and Slimes.
The only thing we know about Brand now is that he began as a wisp of flame sealed within a frozen cage in some cave in Lokfar, the harshest region of the Freljord. A Lokfar marauder known as Kegan Rodhe found the cage in which Brand's flame still burnt. There was something about the fiery light that hypnotized Kegan, which is similar to how Tahm attracted the "Handsome Gambler" with his song. We also know that Brand's origin are ancient, perhaps even as old as the first Rune Wars (which are confirmed to have been waged between the Protectorate and the Magelords who appear in Aatrox's lore). The selfish desire Brand exhibits is to leave naught but burning carnage in his wake.
Since Summoners and the Institute of War are no longer official lore (or atleast not in the way they once used to be), there is very little we can say about the origins of our scary scarecrow. What little we do know is that he inspires fear and dread into the hearts of his victims and then drains the life out of them. It is quite possible that his selfish desire is simply to cripple the will of those around him by inspiring sheer terror into them.
Same as Fiddlesticks, after the drastic lore change we can no longer safely assume that Nocturne simply appeared on the Fields of Justice and was trapped inside a Nexus shard. We can assume that Nocturne persists to be a living-nightmare of sorts who stalks the dreams of mortals, invading the most personal and unprotected parts of their minds. His selfish desire would be to continue invading people's minds and turning their innermost fears into a nightmarish reality.
Besides the fact that his title is "the Demon Jester" this guy had ambigious origins from the very start. Nobody knows where he came from, what he is, and we don't even get information on how long he has been around. What we do know is that he believes death is hysterical, and he is known for regularly commiting horrendous, law-breaking atrocities. He cannot be reasoned with, and his favorite hobbies include jesting, killing and laughing, in that order. Additionally, Shaco, Noc and Fiddles are friends (as the official LoL website would have us believe). One might say it's simply because they all share the Flee mechanic, but in that case, wouldn't Hecarim be listed as one of their friends? I personally believe that these three have something else in common, something deeper, something far more malevolent.
Everyone knows that Swain is accompanied by a raven that is always perched on his shoulders. Although most people might think that Beatrice is just that, a bird, I think otherwise. All we really know is that as an adolescent Swain was always followed by Beatrice and when he joined the Noxian military he semingly had the power to turn into a giant daemonic raven. Beatrice follows him always, but when Swain dies it leaves him without a moment's hesitation. If Beatrice truly is a daemon in bird-fom (similar to how Tahm got his fish form) then perhaps it proposed a deal with a very young Swain, offering him power. It is possible that Beatrice follows Swain for she sees potential in him, a potential to become ruler of all Noxus (which he sucessfully achieved) and perhaps the entire world. Additionally, in Sion's background, at the very end, we see that Sion faintly remembers his General's whispering (Darkwill most likely), a message: "Sion - Beware ravens". So if Darkwill knew about Beatrice, then she is definetly exceeding the normal lifespan of any mortal man, hinting towards her true daemonic nature. Perhaps Beatrice had a hand in the making of Noxus, guiding its rulers and turning the nation into a militaristic empire where strength is justice. That would perhaps be Beatrice's selfish desire, to conquer all of Valoran in a bloody and gruesome conquest.
My final object on the agenda would be the boss of the Twisted Treeline, as well as the God-like being worshiped by Elise and her cult. So far we do not know what EXACTLY happened to the Shadow Isles, only that its King's mind was overwhelmed with grief and that he may have ordered his mages (represented as the West and East Altars on TT) to break the barrier between life and death, which resulted in the entire kingdom becoming the ghastly hellscape we know. Now somewhere along the line, the giant arachnid that provides extended life to his High-Priestess in exchange for Human sacrifice inhabits the same Shadow Isles. This presents us with several questions: When did Vilemaw appear? What is his purpose? How sentient is he? What do the Undead think of him? And of course, is he a daemon? Now, if Vilemaw is a self-aware being and that he instructed her to create the Cult, then his selfish desire is probably to be revered and to receive sacrifice.
So now, as I finish this post, I am obligated to ask you folks about what you think about this subject. Feel free to leave your ideas in the comment section below.