(Third-person perspective)
Aermir smiled. Eddard had made many assumptions, but because Eddard knew him well enough, he could guess most of it. Aermir looked at Eddard's confused face and realized it was time to tell him everything.
The Night's King is real; he commands a vast army of the undead in the Lands of Always Winter.
Eddard was stunned and didn't know how to answer for a moment, thinking that Aermir was joking.
"Don't make fun of me, Aermir. You may be a strong person, and you may not need to give me a reason, but you're my son's age. I hope you can at least respect my age, and I want to have a serious conversation here."
Aermir said with a deathly pale face.
Do I look like I'm joking?
"Are you serious?"
Aermir nodded. Eddard, still finding it hard to accept, said...
"Let's just say it's true."
It's true.
Aermir told him everything that happened when he connected to the weirwood Roots network and convinced him of the Night's King's existence.
"That doesn't make any sense at all. We have a common enemy, why would you fight with the Vale?"
Aermir sighed.
"Because there are no permanent enemies, nor permanent friends, only permanent interests, even the Seven Kingdoms can't be said to be clear on this point. Let's put our hands on each other and have a real conversation about this. Suppose I tell the whole world that the Night's King is real; what would the Night's King and the Seven Kingdoms do? Be objective, don't let your emotions influence your answer. Can you do that?"
Eddard thought for a moment and said.
"If you don't put one of them in front of them, it will take a lot of effort to convince them that they are real."
Aermir nodded.
"That's right, we can't even create the environment for a potential alliance until we catch one of them. That's why I've set up a surveillance network around the Wildlings colony in the far north with one of my familiars. Once I spot them, I'll try to capture one of them as evidence."
He looked into Eddard's eyes and continued.
"For example, if we skip this stage, what happens next? We'll build a unified army under Robert's rule, the most powerful army this land has ever had, right?"
Eddard nodded excitedly.
"That's right."
"Wrong; I told you not to let emotions cloud your judgment, not to speak based on feelings. Be cold and objective. Put yourself in the shoes of the Old Lion, Lady Olenna, Jon Arryn, Prince Doran, or any other cunning lord; prioritize your own interests above all else. What would you do?"
Eddard thought for a moment, then suddenly realized. His eyes widened, and he said...
"They won't do that, but they'll gamble with their future. No, tens of millions will die!"
"Aermi sighed and said."
"Do you think they'd care? As long as their family remains powerful, they won't care about the lives of others. So tell me, what would they do?"
Eddard looked directly into Aermir's eyes, a knot forming in his stomach. Could he be right?
"If you're right, they'll at most send conscripts and ordinary soldiers, retaining their elite troops."
Aermir continued.
"To them, we won't lose to the Night's King. Even if we do, they'll think we'll weaken the Night's King's power, and when it's their turn, they can kill Night's King. For them, it's mainly a matter between us and the Riverlands. They all want us to be the main force in their armies."
Aermir looked somewhat dejected and continued.
"You'll see, I'll find an undead, place it before them, use Robert to unify them, but as you said, this will be an army mainly composed of conscripts and ordinary soldiers. We can't lose to them, because we have our own magic users."
A glimmer of hope shone in Eddard's eyes as he spoke.
"Can you beat him?"
Aermir shook his head.
"I don't think so. He's far too much stronger than me."
He pulled up his pants and showed Ned the purplish-red handprints on his ankles.
"This is Forced Invitation Curse. If I don't block it, he might be able to bypass the Wall, or worse, the Wall might collapse. I don't think I can defeat him in a large-scale battle or one-on-one, but if I can isolate him and use all my spells and techniques, I might be able to defeat him. We're not without hope; I have plans to deal with him, but until I witness his power firsthand, these plans are just plans." Aermir sighed, a thoughtful expression on his face. "I don't even know if these plans will work. A wise man once said that a plan only works until the first arrow is shot."
Eddard said with a thoughtful expression.
"I still don't believe they will hold back their strength when facing a common enemy."
"I hope you're right and I'm wrong, but I believe they'll reserve the majority, or at least most, of their power. Some might surprise us, like the Old Lion who could help us, but he'll likely demand a high price. He's worked for the kingdom's progress, but his family's reputation has benefited greatly as a result. He would never do something for nothing."
Eddard looked confused.
"That still doesn't explain why you're fighting against the Vale?"
Aermir said with a smile.
"In a way, yes; for example, your main force is weakened. Most of your men have died in battle. Do you have the courage to face such a threat alone? Are you willing to take the gamble you're talking about? If we weaken them, then they will send out more of their remaining main force instead of cannon fodder."
Aermir seemed hesitant, unsure whether he should mention the other reason as well; Eddard noticed this and spoke up.
"What's wrong? Are you hiding something from me?"
"Assuming we defeat the Night's King, in the best-case scenario, we will lose two-thirds of our army."
Upon hearing his words, Eddard's face paled.
"Now, after a major war, our army is severely weakened, and on our land lies a poor country with a disunited military. This creates a huge opportunity for certain people. Can you guess who it is?"
He said with a dejected look.
"Stop playing tricks, just say it."
"Okay, faith... I'm 100% sure they'll try to end the Old Gods' rule in the North. Then the Andals can win without a fight after six thousand years, and their long-cherished wish can be fulfilled. Do you think they'll go back without hesitation?"
Aermir's expression grew even more serious as he continued.
"When we are weak, they will not return. Hoster Tully has no guts to do such a thing. Tywin Lannister is too clever to allow believers to join his ranks, but the Vale is the perfect place. Jon may not be a devout believer, and faith may be a tradition to him, but it is not to his lord. The Vale is almost entirely composed of fanatical believers; they will not hesitate when the High Septon commands them to convert to the North."
Aermir looked firmly into Ned's eyes and continued, "Therefore, when the great war breaks out, I want to ensure that the Vale is always on the same battlefield as us. After the war, the Vale needs to become the weakest kingdom, so that for a long time they won't even dare to dream of another war."