System is a catch-all term used by the Imperium to classify the various forms of star system that make up the galaxy. Each system is formed of at least one star and the stellar material that orbits it.
Planetary systems are a minority of the systems that make up a sub-sector. Even within planetary systems with several planets, worlds inhabitable by humans are low in number. Of the ones that are inhabitable, or worth exploiting, the majority are mining, agri and civilised worlds. Relatively few systems possess Forge or Hive worlds, making those that do strategically important. Uninhabited systems can also have strategic importance, depending on their galactic location.
- Armageddon System - contains Armageddon.
- Cadian System - contains Cadia.
- Isstvan System
- Sol System, also referred to as the Terran System - contains Terra.
- Tarsis Ultra System-contains Tarsis Ultra.