Aliphri

The Aliphri are an interesting people. First extraterrestrial species that Humanity discovered, yet one of the last that we learned to communicate with before our little empire came crashing down. First species with what we might call "supernatural powers" as well, being what can only be described as psychic, and immensely so. They're also the only species that humanity can no longer communicate with for the same reasons that prevented communication in the first place.
You see, the Aliphri language is unique in how it functions, relying on the psychic abilities of both the writer/reader or speaker/listener to get meaning across.
Communication could still happen before humanity truly understood their language, but it was widely one-sided. Humans did most of the talking, and the Aliphri nodded or shook their heads in response. That would gimp any political relations, but thankfully the Alphri were understanding. Humanity wasn't the first species that couldn't understand them. In fact, no one had.
As widespread as the Aliphri were, not a single race had managed to communicate with them on their own level. That just would not stand to human scientists.
They spent years and millions of worldwide tax dollars, trying to find some way to get what they needed, whatever it might be. Some tried to enrich the human mind, so as to match the Aliphri in their abilities. Other's tried to develope some sort of equation, or algorithm, or complex piece of coding that would read what they were saying and translate it. That experiment is confirmed to have failed completely.
What finally managed it was a headset and an ungodly amount of processing power.
Through this project, called the Pineal Computer, the effects of a psychic connection could be simulated accurately. Now we could speak to the Aliphri, and boy did they have something to say.
Or so we think. Those conversations are restricted with so much encryption that to this day, no ones broken them. Even spy bugs found having been at it since before our world collapsed have not seemed to have made any progress.
Speaking of the collapse, you can imagine what that meant for the Pineal Computer, no?
Wherever it is, if it's still intact, it's in a vault somewhere deep underground, so hidden we're probably much more likely to find it by accident than through any actual searching. And so, the one race that could understand the Aliphri was once again silent.
They seem to hold out hope that we'll speak to them again, maintaining what contact they can with the governments of the Sol system, but they seem....sad. Like they lost someone close to them, and simply hope that they'll reappear. Their envoys are treated with universal respect, and they always seem to show up at those sorts of watershed moments.
If only their council could be heard.