The Terminus Systems is a region of space in Mass Effect without a centralized government, filled with smugglers, mercenary bands, and slavers. The inhabitants are typically hostile to or at least apprehensive of the governments of the Citadel Council races. While there is no true central leadership in the Terminus Systems, they are often treated as their own faction. It is considered likely that if the Council were ever to take military action in the Terminus Systems, it would provoke the inhabitants to unite militarily and become a major threat to the Council. The most powerful individual in the Terminus Systems is the asari Aria T'loak, who controls the asteroid space station Omega and has enough influence to unite the Terminus Systems' major mercenary groups against a shared threat.
The Terminus Systems have no formal military, but the mercenary groups which operate within have enough power to pose a threat to the Citadel Council if united.