Gaztak

The Gaztaks were humanoid mercenaries, predatory space pirates for hire who were led by Generals. (PROSE: Warmonger)

There were hundreds, perhaps thousands of Gaztak bands. They roamed the galaxy in their battered old spaceships, living on whatever pickings they could find, looting and stealing from anyone weaker than themselves. Grugger's band was typical enough, though perhaps rather smaller than most, as he had once led a little mercenary army in a mini-fleet of battered space-cruisers. (PROSE: Meglos)

Technology
The Gaztaks used large spaceships. These were almost cuboid in shape. In conflict they employed energy weapons such as rifles and handguns. (TV: Meglos)

Under Meglos
In 1980, Meglos hired a band of Gaztaks led by General Grugger to abduct a human from Earth so he could take on its form. They kidnapped a human named George Morris and took him to Zolfa-Thura. Grugger and his aid, Brotadac, were hired to help Meglos steal the Dodecahedron from the Tigellans.

The Gaztaks landed on Tigella where they captured Romana II and had her lead them to her ship. She tricked them by leading them in circles before losing them in a Bell Plant attack. The Gaztaks then attacked the Tigellan city and managed to beat back the defenders, but suffered heavy casualties. The remaining Gaztaks and Meglos later went back to Zolfa-Thura with the Dodecahedron and planned to activate it to destroy Tigella. Grugger and Brotadac decided to double cross Meglos and imprison him and activate the Dodecahedron themselves. However, the Fourth Doctor sabotaged the Dodecahedron, and when it activated, it destroyed Zolfa-Thura, killing Grugger, Meglos, Brotadac and the surviving Gaztaks. (TV: Meglos)

Under Morbius
In the far future, Morbius recruited millions of Gaztaks for his armies to help him in his wars. (PROSE: Warmonger)