Zull
The planet Zull is considered to be "one vast, impregnable fortress", and is inhabited by large, nasty-looking humanoids with leathery skin, tusks and lots of teeth. These are led by Karzai Lorcha, who doesn't mind using the planet's defenses to protect wanted criminals in exchange for their services.
Fiction
IDW Generation 1 comics
The Decepticon Swindle once made a deal with Karzai Lorcha, allowing him to hide from Ultra Magnus on Zull. However, Magnus tracked him down and easily broke through the planet's defenses, took out Lorcha and his guards and captured Swindle. Before leaving the planet, Magnus warned Lorcha that if he ever safeguarded any other Cybertronian criminals, he would "bring the walls of Zull tumbling down". Spotlight: Ultra Magnus
The AllSpark Almanac
Zull was part of the Quintesson Pan Galactic Co-Prosperity Sphere. The AllSpark Almanac II
