A race highly advanced in scientific knowledge, the Kraals are short and greyish-green, their skin hanging in folds over their bodies. They typically wear long metal tunics. The Kraals come from the dusty planet Oseidon, the only planet in the galaxy with such a high level of natural radiation. The radiation level is constantly increasing, causing the Kraals to have to search for a new planet to call home.
One key Kraal science is in the creation of replicas. Using a plastic-like material, the Kraals can create entire planetary landscapes that are almost perfect enough to fool even a native. They are also highly skilled in constructing androids that are exact copies of real people. In order to do this, the Kraals must attach a person to a metal pallet with restraints on the wrists and ankles, and they can then subject the person to a pattern analysis. Although painful, this procedure records and stores the person's entire body pattern as well as all of their memories, from which the Kraals can create androids of other people. The bodyprint is overlaid onto an android framework, and dissolves away if the android is destroyed. Apparently they are indestructible, but they can be destroyed with a prototype Kraal gun although it only works at short range. The androids are armed with projectile weapons in their index fingers, and they also seem to need occasional visits to a recharge unit. They can be stored in large black pods until required.
Among their resources, the Kraals can inflict mental torture on people remotely, although they may have to implant some sort of device first. They can also use the pattern-analysis machine to extract the memory and intelligence of living beings - and if it is left on for too long, it will cause the being's brain to swell until the skull explodes. They can create space/time warps for travel, and use matter-dissolving bombs to destroy their training grounds.
Guy Crayford, one of Earth's astronauts travelling in the XK5 spacecraft, believed that following his launch, his ship was being torn apart by gyro failure. He thought that the Kraals had rescued him and put him back together, aside from his left eye, which could not be found. But, in fact, he had never been injured at all, only hijacked. The Kraals, led by Styggron and Marshal Chedaki, were using him to mount an invasion against Earth so that they could leave Oseidon. To this end, they used Crayford's memories to construct a replica of the English village of Devesham and the nearby Space Development Centre, which they used as a training ground to practice their invasion techniques until they were flawless. The Kraals assured Crayford that they only wanted to occupy the northern hemisphere of Earth and live in peace with the human population, but in fact, they had developed a deadly virus that would destroy the human race within three weeks, then burn itself out, leaving the planet suitable for habitation by the Kraals.
The Kraals eventually sent Crayford back to Earth in the XK5, using a cover story that a stabilizer failure had sent Crayford into orbit around Jupiter. On Crayford's approach, a fleet of the android pods, designed to shield the androids from the G-forces and heat of re-entry, were launched. The androids then attempted to infiltrate and take over the Space Development Centre. Unfortunately for Styggron's plans, the androids proved to be susceptible to jamming radio signals, and he himself was destroyed by his own virus.
