Shuma-Gorath (Marvel Premiere #5 1972): Before all was, I was. Before time was, I waited. I fed on the screaming souls of the Universes. I drank the spoiled milk of dead stars. I am the emptiness outside all understanding. I am Shuma-Gorath.
Shuma-Gorath (also Chtma-Gorath or Cthuma-Gurath) - aka The Great Old One, The Void Made Flesh, He Who Sleeps But Shall Soon Awake - is first mentioned in the Robert E. Howard** short story "The Curse of the Golden Skull," in The Howard Collector #9 Spring 1967.
I may be repeating things here...or not...but I've been discussing the Drowned God of the ironborn on Heresy the last day or so and I am quite convinced that Shuma-Gorath is the greenseer creating white walkers. The kraken shape of Shuma-Gorath is the weirwood root tentacles, and this creature's powers were freed/released sometime before the Starks found their direwolf pups in the snows. I think it is a separate greenseer than Bloodraven, because he should be connected to the ironborn. It may even be Euron, if that is even actually Euron. It may be this greenseer is skinchanging Euron's body and his actual body is below ground.
“Strange soon clashed with powerful demon servants of Shuma-Gorath, a vast extradimensional entity who had menaced Earth thousands of years ago and now sought to return via the mind of the Ancient One himself. At his mentor's prompting, Strange slew the Ancient One, preventing Shuma-Gorath's passage. The Ancient One's physical death made him one with Eternity [the universe], and Strange became Sorcerer Supreme, guardian of the entire universe.”
I read more than one poster that thinks there's another three-eyed crow other than Bloodraven, and it would be cool if this other greenseer sought to enter Bran's dreams through Bloodraven's third-eye. Isn't that what the Marvel version is saying?
So this very old demon was once part of the Nameless Old Gods Beyond Count, and just so happened to demand blood sacrifice from his subjects in homage, until he was rousted from the mortal domain long ago by a powerful sorcerer. But, he returns to terrorize the counterpart to Westeros’ Northern lands in about the same time period as the First Men were thought to have crossed over from Essos in ASOIAF…
This is a nice tie in to the blood sacrifice used in casting magic, and likely another connection to some ancient, great greenseer.
Crom sent a great storm to the Northlands, and with it three iron-bound books and a key to unlock them. He then led a shaman of the Northmen to the books and instructed him to summit a nearby mountain. The Northman first read the books aloud to his kinsmen, then departed for the mountain. Thus armed with the magical tomes, the shaman there confronted Shuma-Gorath, again read aloud from the books, and was incinerated by the demon near completion of the third volume. Before he perished, however, a “flame-headed cloud” rose from the tomes to seal Crom's spell - the cloud destroyed all minor demons, and imprisoned Shuma-Gorath beneath the mountain. The three books became known as the Iron-Bound Books of Shuma-Gorath, and the mountain known as Mount Crom.
Euron did something to unravel the hinge that was keeping magic contained. It would be cool if he ends up with three iron-bound books in his possession.
Strange summons the powers of the Vishanti, opens the Eye of Agamotto, and uses his third sight to enter the Ancient One’s mind - he encounters Shuma-Gorath in an endless abyss and engages in a battle felt by mystics around the world. [Old Dormammu even makes a guest appearance here!] Even empowered by the Vishanti, Doctor Strange could not match the strength of the demon within the Ancient One's mind. Feeling himself losing control, the Ancient One instructed Strange with the last of his power “to destroy that portion of his mind which constituted his ego or sense of self, thus ending his corporeal existence, allowing his spirit to become one with the Universe, i.e. Eternity.” The fate of Earth at stake, Strange was forced to comply, so he summoned all of his mystical will and killed his mentor. When the Ancient One died in the Crypts of Kaa-U (!!!) Shuma-Gorath was trapped in the dead brain, blocked from entering the Earth dimension, and was forced to return to his home realm. As Shuma-Gorath retreated to his own reality, the city of Kaa-U, along with Buddha and the Shadowmen, collapsed in ruins and sealed the crypts for all time.
Another passage that seems to imply that this other greenseer was able to enter and use Bloodraven's third eye to travel into Bran's dreams.
Years later, Strange's talismans [the artifacts of the Vishanti] and scrolls are are almost completely destroyed during a battle with another sorcerer. This weakens the mystic barriers to the dimension imprisoning the Old Ones, allowing them - including Shuma-Gorath - to enter the Earth dimension again.
More stuff to use as clues to try to figure out what Euron might have done in order to unravel the warded hinge holding back magic.