The planet was called Lethe, and it was the single most popular place for beings to go when they wanted to retire from the life they had lived. A person would expect such a place to have optimal climate, and restful views, but Lethe was about as far from that ideal a planet could get and still be habitable. Most of the species in the Galactic Alliance preferred to live in the carefully tended domes, rather than chance the uncertain weather conditions outside. What made Lethe popular, and gave foundation for the name, was the peculiar energy source the natives had devised.
The natives themselves, were akin to their environs, being vaguely reptilian, if reptiles had four legs, two arms, and insect-like jaws. The Jrik-Pha, as they called themselves, more than made up for their fear-inducing appearance with their calm and cheerful demeanors. They were the ones who had contacted the Galactic Alliance about becoming a member, soon after first contact had been made. They then sent thousands of individual Jrik-Pha out into the far reaches of the Allied Systems, to take up service jobs as soon as the paperwork had been filed. In a few short years, it seemed that there was at least one of the fearsome looking, yet friendly and efficient beings on every station and colony.
Jrik-Pha hospitality and caring soon wiped away the fear most people had, and an add campaign, funded by the high council on Lethe, invited the elderly, the war weary, and those who just wanted to get away and forget about things for a while, to come and visit the beautiful domed gardens of Lethe.
Of course people came, and came in the thousands. Not one of them wondering at the odd jeweled pendants that they were handed upon stepping onto the soil of Lethe, as every planet has some way of keeping track of visitors, not all as pleasant, or as fashionable, as the gems surrounded by a copper ring. When a visitor left, the pendant was returned, and although several tried to keep the pendants, the guards at the shuttle gate always found them and retrieved them. In the cases where a being chose to spend their last days on Lethe, the pendent was often reverently removed as soon as the being was dead.
No one bothered to ask where the pendants were taken after, nor did they wonder about why they never dreamed on Lethe, but it was a question whose answer would have caused the booming tourist and retirement industries to bust and dry up faster than a lake in a supernova.
It was the dreamcatcher that was the reason. The one bit of technology that the Jrik-Pha high council had kept secret from the Galactic Alliance, yet was the symbol on every structure a non-native had access to. It was a complex bit of technology with vast networks of underground conduits, but only one simple interface. It resembled a concentric web encased in a ring that was adorned with gears and stones. A short waveform indicator graced the upper right quadrant, while wires ran from the upper left. The pendants that the tourists wore could be attached to this dreamcatcher, and there were enough visitors that the council employed round-the-clock shifts to feed them into the device.
What the pendants uploaded into the machine was all the mental energies that it had gathered, energies that the being would otherwise have spent in dreams, memories, and other idle pastimes. For that was the secret to Lethe's name. While you were there, you could forget things, and the natives wanted you to, for it fed their dreamcatcher, and powered their cities.
Perhaps, some day in the future, someone will find out about the pendants, and the seemingly limitless non-polluting energy source the Jrik-Pha employ. When they do, there will be all sorts of galactic uproar, but that is a tale for another day.