aurelion sol teaser confirms other planets with life

We have alien themed skins, which count in a way, especially since Yordles were supposedly to have traveled to Runeterre on a massive space ship. (It's in the lore somewhere, i don't know where.)

Aliens are anything not originating from your home. Thus any thing from another dimension would be an alien.

Also, I don't know why it hadn't occurred to you before that there could be other habitable planets in Runeterra's universe. For one, many champion's lore mention other planets.

Where does it say that bard is from another dimension... he is a cosmic protector meaning he goes around the universe protecting. Sorry but you should actually read the lore. ATM Malphite, kayle, morgana, and taric are from another planet, thus conisdered "aliens". With the taric rework he might change where he is from, but at this moment, those are the ones specifically from another planet. Only ones from another "dimension" are those from the void.

I did. And yes, the Void is not "another world" in the traditional sense, but all of the Voidborn that have been released so far are very similar to pop culture's definition of aliens. Kha'Zix is basically a xenomorph from Alien, Cho'Gath could be a kaiju, and Vel'Koz is quite similar to the stereotypical "abduct and probe" aliens we had a long time ago. The Void is really just a stand-in for extraterrestrials.

I mean, what would you want to see in an alien champion that the Void hasn't already covered, or couldn't cover?

As I said above while talking to Resumed, while the Void is not a different planet by the strictest of definitions, its beings certainly have an extraterrestrial vibe. Kha'Zix is basically a xenomorph, Vel'Koz is a stereotypical "abduct and probe" alien from scifi, Cho'Gath is a kaiju, etc. So while they're not aliens by the usual definition, they're still definitely not of this world and fill the same niche. Hence my reasoning for believing that we don't need a champion from another planet when those from the Void will do just fine.

From Cho'Gath's lore:

There is a place between dimensions, between worlds. To some it is known as the Outside, to others it is the Unknown. To those that truly know, however, it is called the Void.

So the Void is very definitely not in Runeterra.