And once they've fed the books into the scanner they can call Vanyel and Savil over to come take a look at the decoded version.

Vanyel is awed and kind of scared by how quickly and easily they deciphered a code he spent weeks banging his head on in vain. 

These particular records are in (somewhat archaic) Rethwellani. They're nine hundred years old, a century older than Valdemar as a country; the written spelling has shifted somewhat in the interim but is still comprehensible if he reads the confusing bits out loud.

They contain an abbreviated accounting of Leareth's work in Rethwellan, which already existed as a kingdom at the time, and had the magical Sword of Rethwellan for choosing its rulers, but otherwise lacked most of the features of modern Rethwellan. Leareth (going by a different name) apparently advised one of their monarchs for most of his reign, setting up various monetary and trade policies that seem likely to have contributed to Rethwellan's current prosperity, opening a mage-school in the capital that Savil claims still exists in the present, and formalizing a lot of Rethwellani's legal system into written law. It sounds competently done and none of it is especially horrifying. The journal is mostly a dry list of events and work done, but does contain occasional complaints about how younger-Leareth could absolutely make this happen faster if he took charge himself. 

It is not zero encouraging that on this occasion he did useful things without relying (according to his notes) on mind control but these are also the records he chose to give Vanyel so it's not very much information. It does not leave him delighted about giving the man the power to conquer the world but - well, realistically he can't rule it out. He does not say all this. He does ask for more context on Leareth's invasion plans, why he's invading Valdemar in particular, do they know how he might be - tail lash - seizing control of other peoples' bodies...

Vanyel has no idea why he wants to invade Valdemar in particular! Could just be that it's the closest place to the region north of the mountains, which was probably an easy place to stage an army given its lack of existing state structures. ...Sorry, closest place to the north other than Iftel, but Iftel is protected by a giant miraculous shield barrier and probably even Leareth can't get through that. 

He can't give them anything more on the hypothesized body-snatching, Leareth is especially close-mouthed about his immortality setup. 

What do they think of leaving a note for him? Matirin is conflicted. He would really strongly prefer to have nothing to do with this person if it can be avoided, but it might be that it cannot. 

:Hmm. I'm - trying to decide what he's likely to do if you send a note, and...what he'll do if you don't send a note...: Vanyel looks thoughtful. :It's interesting that he only held onto your scout long enough to ask some questions, and hasn't kidnapped anyone else. I'm absolutely certain he could if he wanted to, and - he has to want your morphing ability, I'm sure he'd have noticed how it shows up to mage-sight and - he could just mind-control one of your people into demonstrating, right... Which he hasn't done. I don't know why, or - how likely it is that he'll change his mind if we just ignore him...: 

Tail-lash. <I do not wish to be at war with this man and I appreciate that he has not yet tried to make it necessary.>

:I bet he doesn't want to be at war with you either, he thinks wars are wasteful and worth avoiding if you can accomplish your aims peacefully, but - I know him. He'd think it unconscionable for you to have technology that could let us feed everyone on this planet - probably you have medical advances too, and whatever else you get with a far more advanced civilization - and not share it. And, morphing would change everything, and - gives us some hints about how the laws of reality must work. I don't know if he could bring himself to let your people leave without trying to learn more: 

<I understand why someone would feel that way. I think the stakes of galactic wars may be hard to convey. If you have to learn the way to the stars yourselves, slowly, millions of people will die needlessly. If you start a war once you get there, trillions might.>

Vanyel ducks his head. Doesn't say anything for a moment. He's trying and failing to absorb the sheer scale of that number. Trillions. 

:He...would understand that: he says finally. :I think you should give that reason in your note. Explain what happened with the Yeerks. He - would get why at the very least that means the onus is on him to prove he wouldn't misuse that power: 

<That makes sense.>

He thinks for a few minutes and then says <I can dictate a note for you, if now is convenient.>

Vanyel arranges himself with pen and paper. :Go ahead: 

<Leareth:

This is War-Prince Matirin-Ashal-Nelinfir. I have the command of the ship that crash-landed on Velgarth. We are giving serious consideration to your offer to help us in the war against the Yeerks. We have two significant hesitations. The first is that we have no expectation you object to the tactics of the Yeerks, given your own employ of them, and are skeptical that you would continue to prefer to work with us once you have reached Earth and could defect.

The second is that presenting you with the resources you have requested would indubitably make it possible for you to conquer other civilizations on your planet, a conquest we understand you to be already planning. The human civilization certain to die at your hands should this come to pass has aided us and offered us sanctuary, and we are reluctant to repay them by enabling their destruction.

More importantly, it is possible that this would present you for the resources to pursue the conquest of the galaxy. Several hundred years ago, Andalites encountered Yeerks on their home world, and set ourselves immediately to providing them with all the technological assistance we could in improving their lives. This went very badly. The Yeerks took us by surprise in a sudden attack and set out to conquer and enslave other peoples. Eight worlds so far have been consumed by this conflict. Hundreds more are potentially at risk. I observed to the Heralds that, while the costs to a civilization of being denied advanced technology are certainly counted in the millions of lives, the costs of enabling yet another galactic conquerer are rather measured in the trillions. 

These hesitations are not necessarily prohibitive and it is our sincere hope that you might have suggestions on how to address them. However, given their significance and potential stakes, we would at this time find it necessary to respond to efforts to learn our capabilities without addressing them as an act of war. This ship is badly damaged, which would make it unusually difficult to limit collateral damage in such a war if it were to occur. Not all of our resources to wage war are on this ship, but the resources elsewhere are even more difficult to use in a fashion that limits collateral damage. 

With due respect,

Matirin-Ashal-Nelinfir>

Vanyel neatly writes out everything as requested. 

:What would you do if he attacked?: he asks when he's finished. :Self-destruct the ship, you mentioned - that probably could kill him if he came in person. My Foresight dream thinks I have to die fighting him, so presumably Final Strike: 

<What is a Final Strike?>

:Um. Mages in our world can - decide to sacrifice ourselves and use our life-energies to make a very big fireball: 

Andalite body language is hard to read but if anything they seem approving. 

<Andalite ships having the living quarters - this part - and the part which houses weaponry. The two parts detach in combat for greater maneuverability. Accordingly this ship does not have the full weapons detachment. Nonetheless were it in orbit we could ensure that nothing survived north of the mountains. There would be seismic activity elsewhere.>

:Would that, um, involve destroying the ship too? And...is there anything you can do if it's still too damaged to get it into orbit at all?: 

<No, the ship would be fine. If we cannot get it into orbit there are...options, but very bad options, beyond causing it to self-destruct. 

If we arrived on Earth too late to save it, and its populace faced unavoidable and certain universal enslavement to the Yeerks, our orders were to prevent the Yeerks from obtaining five billion more bodies through which to conquer more planets. We were given weapons that could be used to that end. I do not want to speak of them in detail. Some of them could be used to target only a specific area but it would carry even more risk than striking from orbit. In truth, my assessment is that use of those options might be worse than letting your conqueror win, but he is aware of them - he asked about contingency plans on Earth when he interrogated our scout - and if he accordingly hesitates to start a war with us and tries to talk with us instead that would be good.

As Valdemar is the country most likely to be affected if he steals weaponry from us, and likely to be also affected by any retaliation, we would of course consult you about what to do.>

...Wow. Vanyel tries not to react with too much obvious horror to the admission that they're, what, planning to just kill everyone if they can't win this war? Wow. 

:I think that should give him a reason not to fight, yes: he says, weakly. Holds up the folded note. :Ready to go drop this off?: 

<Yes.> He will offer it to the person stuck in bird form, who can take it in his beak and fly off. 

<I understand that the plans for Earth must seem - entirely unconscionable. I can attempt to explain more if you would like.>

:Yes, I would like to hear more context on - why that: 

<Yeerks have successfully taken several planets before. What they do is reproduce quickly to ensure that there are enough Yeerks to claim every person in the world as a host. They crawl in through the ear canal and seize total control of the body; the host is conscious, but cannot move or act, and the Yeerk can when desired block their access to their senses. Yeerks take every healthy adult as a host, and kill unhealthy ones; children too young to have the motor control to be useful hosts are kept in good health, though without attention to their emotional or social development, which is not required for the Yeerk to use their body effectively when they are old enough to be infested. They maintain a very high rate of reproduction so that they can quickly vastly increase the number of available host bodies; with humans we have projected that they could double the population every twenty years. The low-level hosts are set to manufacturing ships and weaponry so that the Yeerks can conquer new worlds. No human over the age of four would ever take an independent action again, and within a generation they would not particularly have the opportunity to contemplate it because it has negative effects on people to be raised by neglectful caretakers and enslaved forever at the age of four.>

:...Gods. That's awful. And - they could use those resources to take even more planets, I assume: He makes a face. :I don't suppose you know why they're so -set on conquest? Have your people tried to open peace talks, or at least convince them that's enough planets already?: 

<We know that it is unpleasant to be a Yeerk who does not have a host since their native senses are very limited, and that they have a hierarchy that promotes people for particular success in conquest. I think the prospects of peace with the current leadership are not good since they believe that they are winning.>