According to Gond legend, one day long ago silver men came from the sky. They built a house on the Gonds' planet, and when the Gonds attacked it, the silver men caused a poisonous rain to fall. Hundreds of Gonds died and the earth turned black. The area remained known as the Wasteland, where if one ventured, one would die a horrible death. These silver men were the Krotons, crystalline beings with strong pincers for hands and one large crystal surmounting their stocky bodies. The ship that landed on the planet of the Gonds was part of a Kroton battle fleet that was forced to set down after two of the crew had been "exhausted".
Without mental power, the Krotons were unable to reactivate their ship, so they set about altering the Gonds to suit their needs. The Krotons installed teaching machines in the Gonds' Hall of Learning. The machines filled their minds with knowledge, giving successful students the impression that the Krotons were pleased with them. The teaching machines monitored the students' scores, and periodically the two most promising students were chosen to become Companions of the Krotons. The Gonds saw this as a great honor and allowed their students to go, not realizing that the Krotons were harvesting their mental energy. After entering the Krotons' ship, the students were paralyzed by a force field created by a force generator, which then transfered their mental power into pure energy. The Krotons' ultimate goal was that enough energy would be gathered to operate a thermal switch and enable more Krotons to form from a crystal suspension within the ship. Once the energy of the Companions had been absorbed, leaving them more or less mindless, they were sent out the back way into the Wasteland, where they were vaporized by dispersion units on the ship.
As only the Companions were allowed into the machine, and the Krotons never left it, the other Gonds had never seen the Krotons for thousands of years. They were given all their laws, science and culture through the teaching machines. Orders were given through messages, or very rarely by voice, and to disobey the Krotons' orders was considered impossible.
The Krotons' crystalline ship, called the Dynatrope, is spherical and patterned with hexagons. It must be kept powered at all times, for if it runs down, it will release a colossal amount of energy, causing a huge explosion. If it goes out of balance, the Krotons' heads begin to spin. The Dynatrope absorbs mental power into its circuits, and needs the mental power of four "high-brains" - either Krotons, or other creatures of a comparable intelligence level - to transfer itself back to its own cosmos. As the Gonds have no high-brains and thus cannot supply enough transfer power, the Krotons have no qualms about killing them once their mental energies have been drained. The Dynatrope has a door at either end, operated from the inside by a photoelectric cell. One door is flanked on the outside by two dispersion units, and the other is guarded by a snakelike sensor. This sensor can be programmed with pattern recognition to seek out a particular face. Once it has killed someone, with a gas that reduces people to dust, it retreats.
The Krotons themselves have a lifesystem based on tellurium. Once they are formed from the crystal slurry in their tank, they stay constantly connected to it through a feeder line. The Krotons rarely leave the Dynatrope because they cannot function without being given a direction point, composed of radius and vector, to tell them where to go next. When they do, they can carry a portable dispersion unit. Krotons disperse all waste material as a matter of procedure, including organic beings whose mental energies have been drained. Krotons function permanently, unless they exhaust, meaning that they revert to their basic molecules, although they can even be reanimated from this state. They can, however, effectively be destroyed by sulfuric acid, which melts both them and the Dynatrope.
