Hleno

The Hleno, a.k.a. Invaders or Nuhlenonians, are a sapient aquatic species which evolved on the planet Nuhlenony and were genetically uplifted by the Ancient Ones, better known as the Others.

Biology
The Hleno are naturally aquatic creatures, although thanks to genetic engineering, they have a biological anti-gravity system that allows them to hover in mid-air, as well as the ability to travel via hyperspace, allowing them to move to other worlds without spaceships. Their appearance is similar to a large balloon or dirigible with a jet propulsion system like a squid, yellow eyes and several grasping tentacles.

Although they can breathe air or water, the Hleno can't withstand more than a few hours in dry land and must immerse themselves in water frequently. They speak in ultrasonic frequencies and cannot hear Human voice frequencies. By vibrating their tentacles ultrasonically, they can induce organic life forms to faint and disable robots and other forms of technology.

Their diet consists of processed food created from sea plankton, making them technically omnivorous.

History
Modern Hleno were genetically engineered from marine ancestors by a species known to them as the Ancient Ones, better known elsewhere in the universe as the Others. The Others created advanced technology, including several kinds of robots to tend to the food processing facilities, and were revered by the Hleno as wise masters.

Unfortunately, at some point, the Others' factories started to release so much carbon dioxide into the atmosphere that the resulting greenhouse effect melted the planet's polar caps and caused the oceans to rise and engulf almost all land. The Others left the food processing facilities intact, to be tended by the robots so that the Hleno wouldn't face extinction. But unlike the Hleno, the Others couldn't survive in the oceans and were forced to leave the planet.

Over the next millennia, the Hleno developed into a strangely ambivalent culture, at the same time venerating the Ancient Ones as paragons of wisdom and despising technology, particularly robots. The fact that they still depended on robots and food factories didn't interfere with this view. In a bizarrely well-intentioned gesture to prevent other planets from experiencing the same ecological disaster as they had, the Hleno started to use their own ability to travel through hyperspace to loot other worlds, taking away all robots and other technological devices and disabling those machines that couldn't be simply taken.

Appearances

 * Norby and the Invaders, by Isaac Asimov and Janet Asimov (1985)