Who am I kidding?
It's the background on a race that will eventually appear in an SF story.
The Pak-Tuy are a race of humanoids who are physically indistinguishable from other human races. They are rather secretive about their history, but welcome visitors to their world as long as the visitors don't try to take physical souvenirs. Visitors never stay long, though, because they get the feeling that nothing is there when they're not looking, and that things are constructed as required. The Pak-Tuy joke that their world is infested with "scenery fairies"
Their ships are called "Glyphs," high-speed asymmetric vessels the size of a light corvette, but with the fire-power of a battleship. No one has seen inside a Glyph and all scans indicate they are solid objects with no voids for the crew. The Pak-Tuy say this anomaly is due to their anti-scanning technology.
In fact, there is no race of Pak-Tuy. The Pak-Tuy is a single entity composed entirely of nanobots. Should a humanoid Pak-Tuy be examined under a microscope everything would look human at a cellular level, but deeper scanning would reveal the cell walls are composed of nanites, the internal structures are nanites, in fact instead of DNA they have nanites within nanites.
4000 years ago the planet of Pak-Tuy was involved in a global war. One of the factions devised a weapon that consisted of a small vial of nanobots whose only function was to convert all matter they come into contact with into more nanobots. Unfortunately the nanites converted their holding container into nanites, and so escaped. Five years later that continent was sterilized of all organic matter and consisted solely of nanobots to a depth of 2 metres. The volume of nanites gave the mass sapience: a nanobot entity.
The entity wished to expand, so it began to produce copies of the biological animals it had consumed, birds in particular. The birds flew across the stretches of water that separated the land-masses, and upon landing in the new territory they collapsed into a fine, grey powder: the nanobot's natural state.
200 years after the first release, the last of the organic compounds were consumed by the nanobots. The land, air and sea were entirely sterile. By 300 years the nanite entity was 100 meters deep and covered the world, even spreading under the seas by burrowing through the crust.
"The Pak-Tuy" entity grew bored. It was in a static world and watching the clouds change stopped being interesting after 15 years. It recreated using nanobots the cities and vegetation that had been destroyed by the nanobots. Some time later a passing salvage corvette found Pak-Tuy and, attracted by the high-tech but apparently abandoned cities, landed a crew and shuttle to collect valuable artifacts.
They left soon after having found nothing of value, taking nothing with them except some nanobots adhering to their clothing. Two months later the ship returned after all physical matter, ship and crew, had been converted to nanites. The ship landed on the surface creating the effect of 1000 tonnes of flour being dropped from 500 metres. The new nanobots were incorporated into the Pak-Tuy entity, adding their new knowledge to the whole.
The Pak-Tuy realized that there was a lot more to learn beyond the orbit, and that converting everything it came into contact with would limit the knowledge it could ultimately acquire. It began a programme to neutralize and control the replication process its component nanobots automatically undertake on contact with matter. This programme took 4 years.
It then constructed a star-ladder from the equator to geosync orbit and built another salvage corvette, all from nanites. The corvette collected asteroids to provide nanobot matter to build a space station at the other end of the ladder, and to construct a new class of ship: the first Glyph. This was smaller, slower and unarmed, unlike the Glyphs we see now. The Glyph is in the shape of the ancient Pak-Tuy word that means "recreate" or "renew" depending on context, but on its own it means "recycled."
Visitors to Pak-Tuy are safe as long as they bring their own food. The "scenery fairies" are indeed in action while visitors are present. They are the Pak-Tuy building items for its guests while they are not looking.