Well right now we have at minimum three planes, Runeterra's, the Void, and then some celestial plane of sorts. Assuming there's greater distinctions though then the current situation might look like this:
- Runeterra; all other planes we know of intersect here
- The Spirit Realm: home of demons and spirits
- The Void: likely not always connected to Runeterra
- Soraka's Grove
- Bard's home
- The Gold and Silver City (City that appears at Targon)
- The Glade
- Wherever the sod Aurelion Sol comes from
I'm personally inclined to believe that Soraka and Bard come from different planes given how different they are in terms of their constitution; Bard's a completely non physical entity who communicates in a unique manner while Soraka's much more like Runeterran life, and I'm also wondering if Aurelion might come from a different plane too, considering he seems distinct from both of them as well. Celestial power seems to be the thing that connects them in terms of theme and I feel like that power is related to how the universe and different realities work. The similarity in powers perhaps comes from that celestial stuff being the fundamental power behind the inner workings of the universe and magic, but I dunno. All I know is I'm keeping a count of every weird alternate place and trying to draft up some theories about how this intersecting realities magical friction whatever works.