Season 9
By this time at least a year has passed since the Long Night began and the living have been constantly losing battle after battle, almost always retreating further down south and the White Walkers using the fallen to replenish their army. The cycle appears to not end.
Dany has just been resurrected as unique White Walker immune to dragonglass and will soon be joining the undead siege down south.
Bran has been reading tomes in the Citadel by peering into the past and discovers that wildfire can destroy undead, including Dany if need be. Recalling that his power can in fact influence the past as seen with Hodor and even Ned Stark turning his head around but unable to see him, he tries to change it by convincing the Mad King Aerys II Targaryaen to act swiftly before the Long Night can even happen, but in doing so actually causes him to go mad and over the years this worsens to the point where he can only say one sentence "Burn them all!" shortly before his death at the hands of the Kingslayer.
He also tries to plea with the Night King shortly after his creation but doing so actually causes him to despise all living as weak and sets him on the path to world conquest.
He finally realizes that the past cannot be changed. Whatever has happened will happen and even attempts to change it will actually cause it to happen. The only hope lies in the future.
Melisandre finally makes her way to Jon's camp and pleads with him to take his forces and travel east. Jon is reluctant but Bran agrees they should travel east and Jon ultimately agrees.
Davos plans to execute her but she reveals her true form as a very old woman. Davos stays his hand for now but plans to kill her after the living have won the war. She says only "I'll be dead before the dawn."
As Arya is leaving she remarks "In the end, your prophecy was a lie, Azor Ahai was no one..." Melisandre finally admits their survival was never in fate's hands and that you don't need to a be prophet or visionary to realize the land is doomed.
On the other side of the continent Euron is fighting the dead and they seem to be equally matched. He hears news of Jon's army retreating to Essos and plans to ambush them but doesn't think he can beat two dragons unaware that Dany's death means their questionable loyalty to Jon. His spies however do report of an ancient artifact called Dragonbinder held by the Citadel. With it, he could command dragons and turn them against any enemy.
Gather 20 good men outside the Citadel he calls for their unconditional surrender as the men inside wouldn't be fighters anyway. When nobody comes out he storms the building which reveals itself to be a trap. Everyone is dead and there was never any artifact inside. Euron's men quickly defeat the wights but the Night King himself makes an appearance, alone.
Euron is unimpressed. He challenges the Night King to a one on one fight and promises to **** him up so hard he'll wish he had stayed in the north. The Night King however is equally unimpressed has other plans.
Some time later Cersei grows impatient waiting for Euron to return. Months later he finally does and is greeted by a cheering crowd in King's Landing after announcing that the dead are no longer a problem.
"Finally," she thinks, "another month like this and the people would surely have revolted."
Euron is welcomed in the throne room along with his men.
"Ah Euron, I knew you would..."
She is interrupted by Euron who merely says "You no longer need to worry about any of it, I took care... of everything."
His men proceed to subdue the guards except the Mountain who merely stands still doing nothing as Euron prepares to kill Cersei.
"What is this? What are you doing Euron?"
"Succeeding you, my Queen!" he says as he stabs her in the heart.
Euron Greyjoy, now Champion of the Night King rises only to say "This kingdom will fall! And from the ashes will rise a new order that will shake the foundations of this ****ing world!"
He then proceeds to slaughter everyone in King's Landing and raise them as undead. The Long Night continues...