Jormungandr -- the World Serpent -- is represented by Daenerys Targaryen, who is obviously linked to dragons/serpents, and is in exile, forced to wander the world (the TV show also makes note of how many different languages she speaks as well). Jormungandr is supposedly so massive, he can circle the world and swallow his tail, which is represented by Quaithe's prophecy to Daenerys -- "to go West, you must go East, etc". Another aspect of Jormungandr's character can be seen in Daenerys' relationship to Robert Baratheon, i.e. the Storm Lord with the war hammer -- Thor. In Norse mythology, Jormungandr & Thor are archenemies, slated to kill one another at Ragnarök, and in A Song of Ice & Fire, Daenerys & Robert Baratheon are archenemies (I happen to think Dany will meet her demise at Robert's ancestral castle, Storm's End -- i.e. Stormborn dies at Storm's End -- but that's for a different post). Dany's family was murdered and her throne usurped by Baratheon, and the enmity even followed her across the sea, as Robert tried to have her assassinated, contrary to honorable Ned's advice. What's more is Jormungandr is not just a serpent, but a sea serpent. Dany's relationship to the sea is represented by her need for ships, and future marriage to Victarion Greyjoy. But it is Victarion's Red Priest, Moqorro, who will bring Daenerys, and her dragons, to Bloodraven's side.
Which brings me to Loki's third child -- Hel, the Queen of the Dead. Hel rules over the dead in an icy underworld called Niflheim (reserved for those unfortunate souls who didn't get into Valhalla). She wears a face that is both half-beautiful, and half-dead, and in her role as Sinmara, she's the consort of Surtr, the fire giant.
Surtr, whose name means "the Black", lives at the Bifrost Bridge -- a bridge separating the world of giants from the world of the gods -- and wields a fiery sword, which he will use to set the world ablaze during Ragnarök. It is foretold that Surtr will break the Bifrost Bridge and lead the Sons of Muspell into the realm of the gods to do battle. The Sons of Muspell are fire giants who live beyond the Bifrost Bridge.
Hel & Surtr are represented by Melisandre & Jon Snow. Melisandre currently resides in an ice world, at the Wall (i.e. the Bifrost Bridge), and wears a glamor to hide the fact that she is either extremely old, or already dead (i.e. two faces). She is also an enemy of the Seven, and obsessed with death and sacrifice, constantly searching for king's blood to feed to her fires. And, up until this point, she has provided Stannis with his fiery sword.
Similarly, Jon Snow has "taken the Black" and lives at the Wall, which separates the realm of the Others from the realm of men. And, even though he too lives in an ice world, his relationship to fire is symbolized by Ygritte, who was "kissed by fire".
This probably means that Melisandre will raise Jon Snow from the dead, similar to the way Thoros resurrects Beric Dondarrion -- and Beric, in turn, raises Catelyn -- and convert him to the Lord of Light. She will then become his "wife", much the same as she was Stannis', and Jon will then assume his role as the Night's King (the Son of Craster Jon & Melisandre are holding will draw the White Walkers to them). And in that role, he will knock down the Wall and lead the "Sons of Muspell" (i.e. the Sons of Craster -- the Others -- White Walkers) into the realm to do battle with mankind (i.e. those who worship the Seven -- which is an allusion to Norse numerology -- although it should be noted, the Norse held the numbers three and nine holy, rather than seven. But it's a subtle difference).
We already know that Melisandre feels more powerful when she is at the Wall (closer to Bloodraven), and Bloodraven & Bran have already appeared to her in her fires (the exact quote from A Dance With Dragons is, "A face took shape within the hearth. Stannis? she thought, for just a moment... but no, these were not his features. A wooden face, corpse white. Was this the enemy? A thousand red eyes floated in the rising flames. He sees me. Beside him, a boy with a wolf's face threw back his head and howled" -- Ch. 31. I'm assuming that was the first time Bloodraven tried to contact her directly. But it seems likely he probably communes with the High Priest of R'hllor in a similar fashion). And now, she, and her counterpart, Moqorro, are in perfect position to wrest control of both the forces of Ice & Fire in the name of Bloodraven (i.e. the Lord of Light -- who is a sorcerer -- or rather, the "Last Greenseer". I'm assuming the title was passed down to successive generations of greenseers, and is somehow connected to the Asshai'i legend of Azor Ahai -- which they shouldn't even know, being that Azor Ahai was from Westeros, where the Long Night was fought, far from Asshai. I imagine "R'hllor" first started appearing to them in their fires around the same time the First Men started worshipping the Children and their "Old Gods". Or, at least, that's my best guess, at the moment. Because, I'm pretty sure Azor Ahai is a ruse -- at least in the context that the Asshai'i speak of him. Because, if the Children & Humans really fought the Others together, why did the Children end up on the wrong side of the Wall, with the Others?). Also a subtle clue -- in A Dance With Dragons we meet Benerro, the High Priest of R'hllor, whose skin is milk white (just like Bloodraven's -- perhaps he's trying to emulate his "god"?). He delivers a sermon in Volantis that Tyrion happens upon, and rails against Danaerys' enemies, who he singles out as those who "pray to false gods in temples of deceit" (i.e. those who worship the Seven in Westeros/Asgard -- human gods for humankind, rather than sorcerers and necromancers who grant their followers magical powers).
The role of the Red Priests in the upcoming battle is foretold in another prelude to Ragnarök -- the Three Roosters. It is said that three roosters will sound when Ragnarök begins -- a Crimson Rooster, a Golden Rooster (which will raise heroes from the dead) and a Red Rooster (which will crow at the gates of Hel).
This post was edited on 6/26 at 10:16 am