"There is," he says to the demon, "a way to travel between worlds without being summoned. I will trade you the knowledge of how to make it for three of them and some help identifying a habitable planet in our new dimension."
"I expect to eventually have sufficiently tractable Elves available but am uncertain if I'll have them in a few days. I'll send you the best option available in forty-eight hours."
Nod. "If I find you an Elf who'll do it for a decade, are either of you likely to get attached and disinclined to move on in a decade?"
And he considers for a while and calls someone into his office and tells them that he's been hiding from his people for a long time the activities of the interdimensional collective which has been wavering on whether to oust and execute him, and that Independence is now safely out from under them by coalition with another people subjected to the same treatment, a people who innately have no senses and cannot see or sing or experience the beauty of the world without taking a host. And it is in the interests of this kingdom to help the Yeerks in this brief time before they are independent through the use of daeva, and to help them especially by lending eyes and hands and expertise, and is he willing to give the budding alliance a decade's service as a Yeerk's companion?
It does not take forty-eight hours to find two convinced Elves. He teleports them over to Issiak.
Issiak's new host is nervous, but he served on the front lines of the war against Melkor, facing a fate infinitely worse than death, for King and country, and he keeps reminding himself of this, and he is certainly regarding himself as a volunteer for an onerous duty and not as a prisoner. He promised the King a decade's service and he can do that, assuming they go pretty places and sing occasionally.
The Yeerks get to work building a Kandrona generator; they don't have an infinite supply of the vegetative substitute and it would be nice not to cut it too close waiting on the demons.
Independence throws a festival. Elves are actually more willing than humans to be hosts, both because they're more obedient to their King and because they can keep talking to their friends and working on their projects. Someone determines that you can even enchant metal while a host and at that point there's a great deal of demand for Yeerks, assuming said Yeerks are willing to keep to-be-enchanted rings on their fingers, so the inventors can focus on their enchanting and not worry about sustenance and maintenance of their house and home. Elves are mostly interested in decade-long contracts; the interested humans are mostly not willing to commit that much time.
Midnight writes the peal. Letter to Cam: there's a recording of me swearing to the truth of the contents of this letter. We have no designs on you and yours. We would simply like to live independently of you. If you escalate our peaceful departure from your realm into a war, that war would harm many innocents; if you do not do that, we have no intention of disrupting your governance of people who want to live under you.
And he finds a audio recorder in the lightleaper and swears to the contents of the letter.
There's no response, but then, there wouldn't be.
Two strangers appear in an empty field near a Yeerk pool. Humans, tall ones, a man and a woman, holding hands, both wearing obviously-magical glowing pendants. He's got a coily green thing like a very abstract snake, that tells onlookers about his warm heart and cynical, fatalistic sense of humour; she's got a ripply orange-pink rectangle that tells onlookers about her insatiable curiosity.
When the strangers wake up, they are confused and alarmed!
Their names are Sehana Irtezi Daeredh and Oravith-kelinre Aliharno Tyela. They are from a world called Nuime, which has never heard of the peal, although it's heard of an Arda. They are dimensional scouts. Sehana Daeredh - 'sehana' means refuge or sanctuary - was supposed to keep his wife safe from assorted strange hazards while she hopped them from world to world looking for interesting new places. He has no idea how the stun got past his defenses. He's pretty sure the world is doomed. Tyela, meanwhile, is too panicked to even think about that.