The truth about Soraka's existence.
Ya know, with the VO taunt from our dear space dragon we got some piece of information: that Soraka is an unusual and expetional being, even for cosmic-dragon-standarts. And if we throw that together with what we know of Targon's aspects now...
There seems to be a rule: cosmic entities need a host body to interact with the world. That body can be taken over completly (Pantheon), partly (Diana/Leona) or it can just be a doll to move around (Bard). No clue how Taric fits into this. Probably he's the aspect of a giant gem that was a meteroite or something (maybe that thing came down and created Mt. Targon, making it some kind of "Heart of the Mountain"? Ok, this is getting offtopic.).
Anyways, a host body is needed for material interaction. Aurelion Sol is just a special case because the nature of his power requires him to interact with the atoms and particles of this world to create stars, so giving himself a somewhat stable body should be easy for him - even though he is still half see-through, especially on the low end.
Soraka on the other hand is not an Aspect. She's not taken over by a cosmic being. Her body is not just a vessel - she IS a cosmic being in its own biological shell. She doesn't need a host body to interact with the world. And that might make her one of the potentially strongest entities on Runeterra. Sure, right now she seems quite... young compared to other entities we got to know of, but give her a few centuries and an impulse to learn destructive magic and well... this might not end good for this planet, just saying.
We surely lack a lot of detail in her backstory and it even got rewritten once I think. The only ties she has in lore are to WW and Irelia, also two champions who are old as hell with lore that might not be canon anymore. Heck, Irelias lore might be the most irrelevant thing ever. SHE'S A FREAKING ZOMBIE/LICH and no one even cares? Seriously? The Black Mist eradicated an entire ionian fleet once and no one cares if there is an undead walking amongst them?
Now the big question is if Soraka's current lore is still canon or not...