Vanyel would have been seventeen, Leareth thinks. In fairness to him, Leareth wasn't actually trying not to be terrifying. He was caught off guard and didn't have a lot of time to think of a strategy, but - maybe more importantly, it would have felt like lying to try to seem reassuring and unthreatening to Vanyel (and probably couldn't have worked, when the format of the dream itself made his intentions blatantly clear.) The situation when he met Karal was different – and, after the fact, Leareth can admit that he was less inclined to be upfront about his intentions when his priority was getting off the battlefield and to a place of safety. The dream, for all its ominous stage-imagery, was almost perfectly set up to be a place where neither Leareth nor Vanyel were in actual danger, or had any way to directly threaten each other.
Leareth was also confused at the time, and assigned significant - maybe greater than 50% - odds that this was the last time the dream would happen, because the intended message, whatever it was, had been conveyed. (His best guess was - so that Vanyel would know, not only his destined future, but that Leareth knew, with the obvious implications for how he would be prepared and Vanyel would need to take that into account. Though it still felt very confusing.)
He still thought in depth about what he would say if the dream did recur. It seemed likely to him that if it happened again, it would happen over and over - it would be much stranger for it to happen exactly twice - and, in addition to whatever confounding implications that would have about the goals of the intervention, it would be an opportunity for communication, even negotiation. Which, however confused and suspicious he was, Leareth didn't intend to turn down. His planning for what to say to Vanyel if the dream recurred was mainly on the assumption that it would be the start of a long back and forth.
And then, of course, it did happen again, a matter of weeks later. Again, Leareth has approximately-verbatim notes.
Leareth
Welcome, Herald Vanyel. I was not sure if we would have this opportunity to speak again. It appears that yes. If you have questions, I will answer them. I do not wish to waste my breath on a conversation you are not willing to have.
Vanyel
I’m willing to speak with you. I would like to know what exactly you’re trying to do here. And why. You’re claiming your empire will be a better place to live than Valdemar.
Leareth
I am not sure my intentions will count for anything to you, Herald out of Valdemar. However, I will speak of them anyway. Your Valdemar does not compare so badly, among other kingdoms I have seen, but it does contain a great deal of pointless suffering. You are a Herald. You have dedicated your life to protecting the people of your kingdom, and yet you cannot protect those children that starve in the streets each winter, nor those murdered by bandits on the roads each year. You have seen it too, and it it disturbs you. I would like there to be less of it in the world.
Vanyel
You’re bringing in an army. I know what happens in war. Even leaving aside the people your men would kill, there would be looting, farmers having to abandon their crops. If you want fewer people starving, it doesn’t seem like a good way to go about it.
Leareth
In the short run, yes. It is a cost I accept. Have you ever killed a man to save those he would otherwise kill later, Herald? You have. To protect your people, I imagine, and you would do the same again. I say it is no different if those you save are children who would otherwise have starved in twenty years. I choose the path that will save the most lives, not only now but in the future.
Vanyel
Why lead with an army in the first place? If you really just want to help, why not come to us peacefully?
Leareth
Why do you think I have not tried already? I have been working towards this for very long time, and I have tested every path less costly than this. I now judge that this is the plan most likely to succeed.
Vanyel
All right, assume I believe you about what you’re trying to do. Why do you think you can even do it? You’re not the first person to try to make the world a better place.
Leareth
I know what I am capable of. I have done this before.
Vanyel
That’s impossible.
Leareth
I understand why you might think so. I will lay my cards on the table, Herald, since otherwise I do not see how we can trust one another. I am not a mortal man. I have lived for many centuries. I know the ways of men well, and I have tested my plans thoroughly. Your Queen Elspeth is a good enough ruler, as mortals go, but there is an unfair comparison. She has not the hundredth part of my experience or learning.
Vanyel
Why should I believe you?
Leareth
There is a statue of King Valdemar in the grounds of your Palace. It was carved the year after his death, and has not been altered since; you can confirm this easily. If you look carefully at the scroll he holds, it bears a very large number. I chose that number, and I know the prime factors; that is, two numbers that I multiplied to obtain it. I will tell them to you now. [I did so.] There is another thing you could check. Taver is currently your Monarch’s Own Companion, no? Taver and I met once, a long time ago, and we spoke mind to mind. I believe he will still remember what I said to him. [After a pause] I can offer a final item of proof, and it will serve as a gesture of goodwill. A great deal of lore was lost at the time of the Mage Wars, as you know. I was there, and I remember. I will tell you of a communication-spell I once used. The instructions are as such...
Leareth's main reaction afterward, according to the terse notes he took, is that he was - very impressed. Vanyel might be young and overwhelmed, but he could think on his feet, and ask insightful questions. ...And he seemed willing to talk. Leareth wasn't at all sure that most Heralds would be.
The next set of dream-notes is dated another few weeks later.
Vanyel
I followed up on the information that you gave me. I’m not convinced, everything you offered could be explained another way. Not easily, but becoming immortal wouldn’t be very easy either.
Leareth
I think you are not as skeptical as you try to appear. Nonetheless, I am prepared to act in good faith. It is true that extraordinary claims demand extraordinary evidence. [Demonstrate a map by dream-illusion, the dream allows this.] See this? By this place that you call Horn, under a hill shaped like so, there is a cave. I built and sealed it nine hundred years ago. There is a spell to test the air that will show this, which I will teach you and you may test in other circumstances. There is also a spell you will need to pass through the wards. I will tell you this as well. I placed useful supplies there, that I might use in future, and so I tell you this as an offer of goodwill as well as evidence. [Explanation, pause for Vanyel to memorize this] Is there anything else you would like to know?
Vanyel
I’d like to know how you became immortal. And why.
Leareth
I will not tell you the details of my method, since we do not yet have such a level of trust. I can tell you that it involves magecraft, and that it did not involve preserving the flesh of my original body. As to why, I spoke of this already. You have noticed, as have I, that the world is not a good place. I decided that it ought to be better, and I judged this a goal I could not accomplish in a single lifetime. I also did not wish to die.
Vanyel
What do you intend to do, if the time comes and I’m here at the pass to stop you from entering Valdemar?
Leareth
I will stop you by whichever means necessary, and continue with my plan. I do not wish to kill you, Herald Vanyel, but I will not hesitate to do what I must.
Vanyel
I have another question. If you’re trying to do good in the world, why do you call yourself something that literally means ‘darkness’?
Leareth
You know the Kaled'a'in language? Interesting. That is one translation, but the word has several meanings. One can speak of the ‘leareth’ to mean the night sky. There is darkness there, but also many lights. The lights are those things that matter, and the darkness is what must be crossed. I have always found hope in looking at the stars.
Again, Leareth's notes on his own reactions to this are very sparse, but - he was impressed. He was deeply and genuinely impressed. ...He also wrote that Vanyel "seemed like a deeply troubled and unhappy young man", though - who wouldn't be, in that situation.
(He was amused, he thinks, by the question about his name. In ancient Kaled'a'in it primarily means 'night sky' - you certainly wouldn't choose it to talk about metaphorical darkness-of-character - and Leareth is much more fluent in the archaic version of the language that spawned the modern Tayledras and Shin'a'in dialects. It was spoken in Urtho's Tower, and where he first incarnated after the Cataclysm, and by many of the small groups barely surviving in that first century. His earliest records are mostly in that language, he thinks, rather than his actual mother tongue.)
He doesn't remember anything else about what he thought of Vanyel that far back, though he does remember at least flickers of the conversations themselves. Vanyel's face, trying so hard to match Leareth's controlled calm and give nothing away.