The Faith of the Seven, the religion of choice across most of Westeros, certainly has strength in its numbers–but we've yet to see magic or a miracle directly attributable to them. The Lord of Light has some serious black magic on his side, despite being a less popular religion. He brought Jon Snow back, so there's gotta be something more than tall tales there.

Then there's the Many-faced God, who the Faceless Men have proven must exist in some form, or else they couldn't pull off the magical chameleonic assassinations that they do. And of course, don't discount the Old Gods, who have legions of followers in the North and beyond the Wall. Bran's greensight through the weirwood trees and the powers of the Children of the Forest prove that the Old Gods have power, too.

For that matter, if magical powers like Melisandre's are bestowed by the Lord of Light, you have to wonder if the Old Gods are the ones backing the White Walkers. They were created by the Children of the Forest, and the Children were dedicated to the Old Gods. And there's no question that many of the Night King's skills (like raising the dead or ice-spear throwing) are undoubtedly magical. Some book readers have also suggested there's actually a God of Winter called the "Great Other," who gives the White Walkers their power. If the Lord of Light chooses Jon or Daenerys to be his prophesied warrior Azor Ahai in the war against the Night King, then the winner of the battle between the living and the dead may eventually come down to which god's magic is more powerful.