Aurelion Sol & the Demacian Crest
In Aurelion Sol's lore, the reader is given a rather large journey across the world as the Star-Forger travels in comet form - we get visages of an early Shurima, some hills of greenery, and then we reach Targon. What is important to note is the particular section that details those "hills gently flicked with greenery."
The desert below fades into the night trailing behind me as I streak onward across lonely steppes, then over rolling brown hills gently flecked with greenery. The pastoral scenery belies a field spattered with blood and littered with the dead and dying. Survivors hack away at each other with rough-hewn axes and scream battle cries. One side is losing quite badly. Stag skulls rest atop pikes stuck into the soil, next to writhing warriors. The few still on their feet are encircled by soldiers riding great shaggy beasts.
Those defeated, surrounded few see me and valiance seems to surge through their veins. The wounded rise and grasp their axes and bows in a final stand that throws their foes off guard. I don’t linger to see the rest of the little clash play out because I’ve seen this scenario unfold a thousand times: The survivors will scratch my comet likeness onto their cave walls. In a thousand years, their descendants will fly my image on banners and undoubtedly ride into a tediously similar battle. For all their efforts to capture and record history, one ponders why they do not learn from their mistakes. That is a lesson even I have had to suffer.
So why was this little battle in a seemingly unknown location (and little context) given two paragraphs of a cosmic dragon's lore?
Because of what he inspired just by passing through.
Does this look familiar to you? http://vignette2.wikia.nocookie.net/leagueoflegends/images/e/e3/Demacia_Crest_icon.png/revision/latest?cb=20150602172037)
It should - it's the Demacian Crest. And while some might take it to be an artistic representation of a Demacian Eagle's wing, the real answer may be more simpler than that. I believe that the crest is the comet form of Aurelion Sol. The color is a clue; it's blue, like the star-forger himself. Then, we have the shape of the crest itself; a spherical shape is present in its center (I assume this is the form he takes when in comet form; gameplay-wise his model is retained for consistency purposes, in my opinion. Think teaser video), and then we have the comet's tail trailing behind in three pieces, with the top tailpiece artistically combined with the comet's coma (the atmosphere around the comet).
tl;dr - Aurelion Sol, while traveling to Mt. Targon many, many years ago, inspires some people to win their fight. These people would later become the Demacians. Their descendants then ride his comet likeness on their crests and banners.
Most likely not entirely accurate of a theory, but there was an inkling of possible correlation. If you'd like, feel free to comment on what you think about this theory.