Theory: The game and story are still connected.

Back before the retcon, even though I wasn't around (sadly), the game and the lore were one in the same. Now it seems we're just selecting characters from the lore, and not the actual champions themselves are being summoned.

My theory is basically = summoners are being reworked to a different figure type. Possibly a very powerful inter-dimensional 'police'. The arenas are the areas where fabled figures are drawn to decide the fate of realms themselves. I believe this happens when the backstories of the champions end. 'Summoners' may be responsible for the creation of league's universe, and they alone decide if a realm is devoured by another (Ex: the void.)

When a champion's backstory ends, there is nothing that states what happens next. Therefore, this cataclysmic event may be the void's full invasion. The Void could be the "undefeated champion realm" or something. I'm not sure if this theory will make any sense, but I decided to type it out anyway.

One hole in this theory is to explain why the 'normal' realm's beings can fight the void's beings. I don't have any argument that's solid for this, besides that the void's beings may only fight for the side that has the strength to control them, or they may not be loyal down to the wire.

I'd love to know some other theories.