Eclipse
An eclipse occurs when one body obscures light from another body. The best known phenomenon of this type is a Solar eclipse, which occurs when the Moon passes between the Earth and the Sun, blocking the Sun's light from a region on the planet's surface.
Eclipse in Mass Effect
In Mass Effect, Eclipse is a mercenary organization that operates in the Terminus Systems.
Organization
Eclipse was founded by an asari named Jona Sedaris. Little is known about the larger Eclipse network. Eclipse cells operate on various planets under the direction of a local officer, who supervises their operations. In addition to mercenary work, they are also active smugglers of weapons, drugs, and fugitives. A typical Eclipse cell is a commando unit that emphasizes the use of mobility, biotic powers, and combat engineering (tech powers).
Membership
Eclipse recruits humans, asari, and salarians; most leadership positions are held by asari. In at least some cells, an Eclipse recruit must commit a murder to earn his or her uniform.
Threat Assessment
Eclipse is a significant force in the poorly governed Terminus Systems, but their forces are far too limited to threaten a major planetary government, let alone an interstellar government.