Who are the Summoners (not the players)?

From a lore perspective and not game mechanics stand point who are the Summoners? Sure we the players have Summoner spells and we send the champions to fight on the fields of justice, but who are these beings who pull on the champions strings? What is their motivation? Did all the champions of Runeterra perish long ago, and the Summoners are what left of the remnants of Runeterra. Maybe the Summoners destroyed their world and what they have left is the Eternal game? Are the Champions caught up in a never ending heaven or hell (depending on their love or hate of fighting), or is it some sort of test? Do the Summoners exist outside Runeterra's dimension? Are they the ones responsible for creating the Void, and are they now trying to seal it up? What are the realm of possibilities? Or is it better to just leave this question unanswered?