Kaagh

Commander Kaagh the Slayer was attached to the Tenth Sontaran Battle Fleet's Special Assault Squad. He was the lone survivor of a failed invasion of Earth by the Sontarans.

Avenging his Race
When Luke Rattigan destroyed the Sontaran flagship, (DW: The Poison Sky) Kaagh's space pod was sent off course and crashed down to the planet Earth. Despite damage to the ship and exposure to G-force which might have killed him, Kaagh survived, suffering a large scar down the right side of his face, a similar scar on his right hand, and lost a piece of his right ear. As part of the Special Assault Squad, Kaagh's purpose was to infiltrate deep behind enemy lines in order to predict and anticipate their movements.

Kaagh hoped that by doing this he could make up for his fleets failure to conquer Earth. He began to began a covert attempt at destroying Earth and make himself a hero, "Kaagh the Avenger", then "Kaagh the Destroyer". To this end, he used a neural control implant on Professor Nicholas Skinner and his daughter Lucy, both of whom ran Tycho, a radio telescope nearby. Kaagh planned to use the telescope to bring down Earth's many orbital satellites in a coordinated attack on the planet's nuclear power plants, which would have rendered the planet uninhabitable.

His plan was discovered by Sarah Jane, her son Luke and their friends, Clyde and Maria. Kaagh attempted to kill her and her young friends whom he considered as "half-forms". However, before his plan could come to effect, Kaagh was attacked in his probic vent by Maria's mother, Chrissie, and forced to return home to Sontar in his scout-ship. However Sarah Jane suspected that he would one day return. (SJA: The Last Sontaran)

Partnership with Mrs Wormwood
Too ashamed to return to Sontar, Kaagh began working as a mercenary for the Bane, who had found the consciousness of Horath and used Kaagh as a go between for its transportation from planet to planet. A few weeks after this he met Mrs Wormwood, a member of the Bane family whom had been cast out for her actions. He found that there was a high price on her head, but she persuaded him to help her control the universe. They both plotted to become Emperors of the Galaxy.

Mrs Wormwood travelled to Earth, closely followed by Kaagh, who came in during a siege by the Bane Kindred. He found Mrs Wormwood and killed her attackers. They then stole Luke and the Tunguska Scroll, which would show them where Horath was buried. Luke escaped, but Kaagh managed to catch him. However, Mrs Wormwood was growing tired of him. In the end, she offered Luke a place at her side and double crossed Kaagh, calling him a blundering idiot. Eventually he saw the light and in a last ditch attempt at honour he threw himself and Mrs Wormwood into the portal to Horath's body. (SJA: Enemy of the Bane)

Capturing
He was captured by the Krulius, who hunted aliens, and was digitally stored in his ship. The Krulius was determined to keep Kaagh and the other aliens safe. (WC: Monster Hunt)

Equipment
Kaagh displayed more advanced Sontaran technology than previously seen during the ATMOS factory incursion. He had a smaller, more compact blaster weapon, which seemed to have different settings. He housed his gun in a pocket, which was connected to his leg. He also had an automatic helmet that could retract into his armour and a personal cloaking field. He also employed the use of neural implants, as opposed to the more common hypnosis methods Sontarans tended to use. Kaagh sent out drones that resembled large plasmic spheres to act as scouts, but also had attacking ability. (SJA: The Last Sontaran)

His communicator could be used to control his drone and neural control implants. (SJA: The Last Sontaran) The communicator could also power other electronic weapons such as sonic disruptors. (SJA: Enemy of the Bane) It also was able to tell Kaagh if there was someone on his ship. (SJA: The Last Sontaran)

Behind the scenes

 * Kaagh's cloaking field bears similarity to the cloaking devices used by the title creatures of the Predator film series.
 * Kaagh is the first recurring Sontaran character in the Doctor Who extended franchise.