After reading Aftermath: Empire’s End, I have learned that Imperial Fleet Admiral Gallius Rax is not Supreme Leader Snoke. The reason for this is because he died during the Battle of Jakku. So if Rax is not Snoke then who is? The book also revealed that Darth Sidious sensed something ancient and dark calling him from the Unknown Regions. He seems to believe that this presence is the source of the dark side of the Force. Apparently, the dark presence was calling Sidious alone because not even Darth Vader could sense it. This could mean that Supreme Leader Snoke is a reimagining of Abeloth, who was a being of pure dark side energy so powerful that not even Luke Skywalker himself could defeat her on his own. Now that I think about it, Snoke does somewhat look like the Son from The Clone Wars show. Even though we clearly see the Son die in the show, but since he is an incarnation of the Force it is possible that he cannot truly die. Perhaps the Son was resurrected but in an extremely weakened form. Hopefully, we will find out either in Episode VIII or IX.