The aliens arrived in the Whell star system at a critical time in the development of Whell civilisation. Whells had for tens of thousands of local years inhabited every continent of their planet — which they considered to be immense — but only in recent centuries had developed travel and communications technology to begin to shrink that distance. Whells had established numerous diverse societies, some benefiting from significantly more advanced science and technology than others. As their world figuratively shrank, friction began to develop between the pockets of concentrating power and the pockets of everybody else. Conflict was not an unknown notion among Whell culture, but the scale of conflict which was becoming possible was becoming alarming. Conflict on a scale which had the potential to demand a whole new word to describe it. Mechanised conflict.
Then a scientific discovery was announced. An artifact had been detected on the outskirts of their solar system, in a resonant, periodic orbit much like a known class of asteroid, but with numerous very un-asteroid-like features. It emitted radio bursts, and occasionally long plumes of heat. When the Whell's best telescopes focused on it, they saw an absurdly distant pale blur, too far to reach with a space probe in anything less than years, but visibly far too bright and regular in its aspect to be a simple piece of rock. And then it changed velocity.
And then, in an eyeblink, it crossed their whole system, and slotted into a medium-altitude orbit above their equator, and begin to send messages of greeting.
The aliens introduced themselves as the Ruyk. They had significantly more advanced technology than Whells. Moreover, they explained, they had existed for thousands of years, and had explored all over the galaxy, and had met other civilisations at similar levels of technological advancement many times. Galactic civilisation, the Ruyk explained, was unbelievably more vast, advanced and complex than the Whells had ever imagined. It was a bustling society of millions of other intelligent civilisations, nearly all of them vastly more advanced than Whells, and the only thing allowing Whells to stay beneath notice was their insignificance. The Ruyk offered the Whell species assistance, guidance, mentorship and protection.
Nothing was requested in exchange, which plenty of Whells thought was extremely suspicious. The Ruyk reassured the Whells that this was pure altruism.
But, the Whells also realised, though they didn't make a big show of it, the Ruyk were vastly more powerful on paper — able to cross interstellar space, at least. And they only had the Ruyk's word for it that the rest of the galaxy was any particular way, but no other potential allies were in evidence. It did not appear that the Whells had too many options.
Anyway, the civilisations got on well for some centuries. Whells had not yet developed space travel and the Ruyk would not take them out into space, or further than the Ruyk ship. Still, there was significant common ground between the two of them. They were both tripedal, and they could, with some effort and some suitable protective clothing, briefly, share a common atmosphere and temperature. And their languages, some of them, were similar enough to be learned. This meant that it was possible to meet and chat in person. A long-lasting friendship between the two civilisations developed.
So, within eight local years, did a war. Not a war between the Ruyk and the Whells, everybody knew that that was not a thing which could ever happen, or at least not happen for too long, but a war between one Whell culture and another. The Ruyk attempted mediation between the two parties, but sided with neither, and talks broke down badly. The outbreak of war was rapid and obvious, but hostilities ended agonisingly slowly over the course of almost another century, flaring up off and on, and never really reaching a point of peace, no matter what the Ruyk did.
Later, as this war was fading, the Ruyk shared an astonishing new piece of chemical technology with the Whells. This energy generation technology would draw a particular naturally occurring insulating gas out of the Whells' planet's atmosphere and turn it into energy (and small, radioactive pellets). The Ruyk suggested numerous industries for which the Whells' planet's natural geological and environmental resources could be used. They provided mining equipment, diplomatic intermediaries, cash, philosophical advice, and even exchanged cultural materials: art, "music" (which was two very different things to the two species, but not entirely impossible to re-interpret), and vellum, an art form unique to the Ruyk with no obvious analogue among the Whells, but which captivated the Whells' attention.
In fact, it became a species-wide obsession, crossing internal national and cultural barriers. Vellum displaced many other forms of Whell culture.
The Ruyk tried to scale back how much vellum they were sharing with the Whells, limiting what they transmitted to an extremely small, carefully curated selection of only the weakest examples. Then they changed their minds, and briefly gave the Whells full access to their entire library. Then another war broke out, and one entire Whell culture became fatally transfixed by one of the most extreme examples of vellum art: their culture ground to a halt, and never started up again. At that point, following requests, the Ruyk cut the Whells off.
After many years of this, a senior Whell official managed to corner a Ruyk ambassador at a diplomatic event held on the Whell planet. The Ruyk were extremely tall, flimsy, slender tripods by Whell standards, and would wear thick, warm coats and respirators on the cold Whell planet. They could stay down there for a day or two without significant discomfort, provided that they had places to lie down, and climate-controlled lodgings.
"Rheyuk," the Whell official asked. "Your species has been kindly mentoring our own for almost eighty-one years. We are eternally grateful for the gifts and the guidance you have provided us. Without your kind intervention, and your feats of protection, Whell civilisation would be just a discarded, helpless crumb in the void."
Rheyuk shifted their sharp, elongated shoulders, forming the equivalent of a smile. "It has been our pleasure to watch our protégés mature."
"Rheyuk, the time has come. This building has been sealed. Peace between our species has existed for so long that you ceased to bring security escorts years ago. We have neutralised your fabled self-defence technologies, those which genuinely existed; many which you claimed to have, and not to be able to share with us, proved not to exist."
Rheyuk's shoulders moved again, this time into a nervous grin. "Time for what?"
"In all our years, we have never met another extrasolar civilisation. Not one except for you. We have asked you and you have provided us with indirect contact and recordings of these other civilisations which rival yours in capability. You call them immense, benevolent, highly optimised civilisations, with unlimited material power. But you never let us meet them ourselves. You will not take us into deep space."
"Protection," Rheyuk said. "You know our own mentors manage those relationships for us."
"And nobody but Ruyk people have ever visited this system."
"Indeed, this is a distant system. One of billions. The probability of us stumbling across you was negligible in the first place. You were very lucky."
"Rheyuk, how many species have the Ruyk mentored? Mentored to a point of maturity, I mean."
"Tens of thousands," Rheyuk said.
"Rheyuk: our planet is actually not doing very well. We have severe societal issues which we did not have before you Ruyk arrived, many of which we can affirmatively state arrived with you. We have problems of resource consumption and sustainability, due to decisions we made at your direction. The temperature of our planet is changing. Its magnetic field is changing due to excavation of magnetised minerals for use in entertainment. We have clearly-delineated countries, with borders: your idea. We covered the dead continent with a useless scrub grass which you said would be edible and turned out to be impossible to harvest."
"Our ecological models are largely faultless," Rheyuk said.
"Rheyuk, we are able to detect when your kind are lying. We have been able to do this for some years now and we have been waiting for an unguarded moment. Tell me the real number of species."
"What? ...We have mentored four species."
"To maturity? To the point of equivalent technological and social sophistication as yourselves?"
Rheyuk's shoulders coiled. "Well... technologically? None. Socially? It's kind of a wash."
"Socially, when we started out, you were about where we were. Now you're kind of a step above us."
"Give an account of yourself," the Whell official asked. "I have more tea. I know how much you enjoy it. More tea, in exchange for the full truth. Where are you from? What is going on here? What resources are you trying to extract from us?"
Rheyuk rattled their throat. "You're practice," they said. "You see... we're kind of a big deal. There are more powerful civilisations. But they won't pay any attention to us. We should be rubbing shoulders with them. But we need to prove that we're worth it. We don't actually have a mentor species of our own. We're working on it. But we need practice. We don't actually know how to mentor another species. We're not trying to extract anything from you but experience. We need a positive result. Something we can put in the portfolio. We've given you the best advice we can."
"But that advice isn't very good! It's not a whole lot better than our own best guess, most of the time. Often we discard our own guess and take yours instead."
Rheyuk contracted a little. "We give you our best advice. We tell you to do things the exact way that we do things on our world."
"World." Some embarrassment.
"How is it working out for you on your world?"
"Not amazingly," Rheyuk said. "That's also why we need practice. We can cross interstellar space. We cracked that problem. But everybody we ask tells us that that was a dumb piece of luck. Everybody ignores us, because statistically, there's two ways to get across interstellar space. One is to develop a full-fledged, stable, sustainable society, which can survive for the long term in space. The other is to randomly find the right answer way earlier on in your development, and take off very immature. And..."
"These higher mentor species are real?"
"Yes, and they ignore us, because they know within a few centuries, we're just going to go away again. Civilisations like ours just aren't structured right. They have mentored species to successful maturity before. They do have tens of millennia of experience. They know what it takes. And they think we're a lost cause. So, we're working on it. We're practicing on you."
"And four other species?"
"Three others. You're the fourth. The other three..."
"Got run into the ground, by making all your same mistakes?"
"Something like that. Also, quite a lot of Ruyk think we're doing it wrong too."
The Whell official thought deeply about this. And then, all Whells thought deeply about it. Finally, they told the Ruyk to buzz off, and figured things out by themselves for another millennium.
When an actual mentor species showed up to welcome them to the real Galactic Civilisation, they turned them down. They were doing okay by themselves, thank you.