Rito, I think you ought to to focus less on mythos and supernatural in Runeterra
I really like the League Universe thingy you done now, but I can't help but notice that now you shove Yordles into magical creatures from another dimension trope, and I believe we really have enough of it by now. Mind you that by mythical, I mean mythical to the normal people of Runeterra - so, things like magic, magical creatures and the like are usually just standard stuff. It's the stuff that is a legend, that nobody knows if it really exists (or they exist in another dimension) that I count (so, Voidborns definitely belong on this list, but neither does Kassadin nor Malzahar - as they are humans touched by the void).
- Void - possibly the oldest faction out-of-this-world, and generally a fine one. Having a terror of invasion of otherwordly monsters is always cool. Champions from the void:

- Shadow Isles - the entire existance of this place is a legend, and it's basically an island full of undead (?) with a tragic history. Champions from the shadow isles:

- Aspects - whole mount targon might be a myth (again), and aspects are clearly stuff of legend. Aspects:

- Gods - hell, this needs no explanation. Champions:

- Other mythical beings - includes every other ones that have no clear affiliations to factions/types. Includes:

- And now Yordles are becoming mythical creatures too, so:

That's 33 champions being basically unicorns. I'm totally fine with having some of the champions being a part of myths and legends, but I think this is a bit excessive. And hell, I didn't even count those unknown ones, like Fiddlesticks or Jax - they could turn out like this too.
I'm, of course, posting this because of the Yordle thingy, because they are one of my favourite fantasy races from video games as a whole and the reason why they were so special is because... they weren't special.
Most games try to make their small race to be a bunch of magical people, that have tremendous magical power and basically live in another world. Yordles were just small, and had nothing but their wits and a very safe position on the map (Yordle Lands were separated by a mountain range from the rest of Valoran - and between the mountain range and the rest of civilized part of valoran lied Icathia, Shurimian desert (both infested with Void creatures) and Kumungu Jungle (full of Teemo shrooms and Rengar). While a bit mysterious (and possibly being aliens?) they were still flesh and blood (or fur and glee according to Vel'Koz).
Dunno, I just feel like we've had too much of those mythical champions and we're missing some nice stories on actual lands.