Kraal (species)

The Kraals were a race of advanced humanoids native to Oseidon.

Biology
Kraals were humpbacked, gargoyle-like humanoids with lumpy, grey skin, unusual facial ridges and a rhinoceros-like horn. They generally wore striped tunics. (DW: The Android Invasion)

Technology
The Kraals had a wide variety of technological devices. One of the most popular was their androids. These androids were made in the form of a specific person, generally a human. They had most of the memories of the subject, but were bullet-proof and loyal to the Kraals. To create these androids the Kraals had to scan the subject's brain, or someone who had dealt with the subject. This scan was very painful and could cause brain damage if it went on for too long.

As well as androids, the Kraals also had advanced genetic modification techniques and replication techniques. They could create a deadly virus or recreate an entire village out of the memories gained from a brain scan. (DW: The Android Invasion)

History
The Kraals lived on a doomed world. Oseidon was becoming more radioactive, reaching critical levels. They abducted a human astronaut, Guy Crayford, and scanned his brain. They created many human-like androids and an entire British village from his memory. After testing these androids, they planned to send them to Earth with a deadly virus to infect and kill all of the humans. This plan was stopped by the Fourth Doctor when he was able to stop the androids with Space Defence Station's radar dish. (DW: The Android Invasion)

With the help of the Master, the Second Kraal Army attempted to invade the Earth again, by using a wormhole that the Master generated in Derbyshire. Upon arrival on Earth, the Kraals, led by Marshal Grimnal, double-crossed the Master and imprisoned him with Leela, while they sent the Doctor to Oseidon to be interrogated by Chief Scientist Tyngworg. Grimnal allied himself with the Master's former ally, Colonel Spindleton, as they drew out their battle plans. Grimnal allowed Spindleton to take possession of Great Britain after the invasion, in exchange for knowledge to conquer the world. However, while this was going on, the Master and Leela escaped through the wormhole, and infiltrated the Kraal bunker. However, while he was in the bunker, the Master discovered he was an android duplicate, ever since he arrived in Derbyshire, and the Master had been on Oseidon all along, impersonating Tyngworg. During this, the Doctor escaped and reprogrammed the androids to destroy the invasion force. But, as the Master tried to deactivate all the androids, he discovered he was susceptible to the signal, and therefore, he had also been an android all along as well. After the destruction of the Second Kraal Army and the androids, Grimnal was the only surviving Kraal. He allied himself with Leela and the Doctor, so he could stop the Master's real plan, which involved destroying Oseidon. While trying to stop the plan, Grimnal was shot by Spindleton, but the Master's plan was foiled. (BFA: The Oseidon Adventure)

The Slitheen family sometimes disguised themselves as Kraals in their attempts to make money. (NSA: The Monsters Inside)

Behind the Scenes
According to The Brilliant Book 2012, a non-canonical REF book, in 1881 they attempted to replace Prince Bertie with an android duplicate, but the Doctor and Jenny stopped them.