10 years. 10 years since the human called Jon Snow last saw the Wall.
It seems like it was yesterday, the Accident:
Flashback
Robb and Jon were running in the castle of Winterfell.
"First to the godswood, Jon!" said the young heir of winterfell
"You bet!"
Half an hour later, they were both near the pond, looking at the sky.
"I don't care what my mother say, Jon, a Snow or a Stark, you are my brother".
"Forever?"
"Forever."
And that would have been true if not for their stupidity.
"I bet i'm a better climber than you" said the young bastard. "First at the top of the Godstree!".
"As a Stark from Winterfell, I can't let this challenge unanswered".
Every humans make errors and Robb made one. And falled. The last time Jon saw him he was in his chamber, unconscious. Lady Stark in her rage cast him out of the castle. When Lord Stark came back, it was too late.
"Look at what we got, guys!" said one the men, Jon didn't know then but they were wildling. They were in the South as scout. Under the orders of Mance Rayder, the King beyond the Wall.
"His clothes are ones of a noble, Mance will be happy".
"Yes, now we should go back to Mance, our mission is finished".
"Mance will also be happy to hear about the gate under Fort Nox".
When they arrived beyond the Wall, they weren't welcomed by wildlings, but by great white men, with blue eyes and great shiny blade. These strange men killed all the wildlings, before taking Jon Snow with them. It was the last time th Bastard of Winterfell was seen by a human.
Flashback end
A young girl, not even 10 moon, he was half her age when Jon Snow died and BloodSnow was created.
She could have been changed but she was a female, and there must never be again a Night's Queen.
"Three crows, one hours South." said one of his compagnons
"We will wait them here, it is time they learn that the North is not for the humans" said the bastard turned immortal.
AN: So this is just an idea based on the episode from this monday "Oathkeeper". For the incults the Night Queen was a woman extremly pale with bright inhuman eyes who corrupted a lord commander of the night Watch and make him become the Night King. She and he spilled blood in the Gift with the helped of enslaved nightwatchers. they were killed by an alliance of the King of the North and the King beyond the Wall.
I wrote it with the hope that somebody with more time will make a far better story than i could. It could also be somebody like aegon (he survived by being gifted to the Others), or any kid or baby in Game of thrones/A Song of Ice and Fire