|Voice Actor||Peter Jessop|
Sovereign (Or Nazara) is the massive dreadnought of the Geth fleet, led by the Rogue Spectre Saren. The dreadnought is 2 kilometers in length, with a huge mounted gun with enough ferocity to rip through the kinetic barriers of any other ship with a single shot. Sovereign has the ability to generate mass effect fields powerful enough to land on a planetary surface. This implies it has a massive element zero core, and the ability to generate staggering amounts of power.
 Mass Effect: Revelation
Sovereign was discovered orbiting the Perceus Veil in 2183 by a survey team lead by Edan Had'dah, a batarian entrepreneur. Had'dah began to search for an expert to help him to understand the mysterious ship. His search eventually led to him seeking the help of Dr. Shu Qian, who was formerly Alliance personnel. The two were not ready for the indoctrination effect that the ship possessed, which eventually drove them mad with obsession.
Saren, who in the middle of an mission for the Council, heard news of the supposed relic. Believing he could use the ship to cripple humanity, he began to hunt down its location. Upon coming into contact with Had'dah and Dr. Qian, Saren killed them, stealing their research in the progress.
 Mass Effect
Saren eventually found Sovereign, learning that the ship was actually a sentient machine. Saren learned the truth of the dreadnought, it was a Reaper, a race of sentient machines that return to the galaxy every 50,000 years to destroy all life. Saren allied himself with Sovereign, believing that if he could prove that organics were useful, they would be spared from the coming onslaught.
Saren was able to convince the a number of Geth that Sovereign was a god, that could advance their technology. They believed Saren to be the "Prophet" of their "god". However, Sovereign was offended that the Geth revered him. It believed the Geth to be mere tools that can be used to achieve its goals.
After thousands of year of hiding, Sovereign unveiled himself to the population of Eden Prime. It believed that using the Prothean Beacon would allow it to find the Conduit, a back-door into the Citadel. However, the beacon was programmed in a way that machine could not interpret it. Instead, Sovereign sent Saren with an army of Geth to capture the beacon. However, a squad of Alliance marines were able to send a distress call to the SSV Normandy, along with a recording of Sovereign.
Sovereign returned to Virmire, where Saren had built a Krogan Cloning Facility. When Commander Shepard attacked the facility, he was contacted by Sovereign. It claimed that Shepard attempts to prevent the Reaper invasion were in vain. Sovereign then tried to reach the Facility to attack Shepard. However, Shepard was able to destroy the Facility before Sovereign arrived. He was also able sway Saren's loyalty to the Reapers. Following this event, Sovereign placed cybernetic implants into Saren, indoctrinating him into becoming loyal.
With the help of Shiala and Matriarch Benezia, Saren was able to learn location of the Conduit on Ilos. Saren led an army of Geth to capture the Conduit, while Sovereign led an fleet of Geth ships to attack the Citadel. Saren was able to travel through the Conduit and closed the Citadel's Wards around Sovereign. The Reaper then attached itself onto the Citadel Tower, which it began to use as a method of opening the Mass Relay into dark space, where the Reapers were in hibernation.
However, Shepard and his squad followed Saren through the Relay. Shepard confronted Saren which resulted in Saren's death. Shepard was able to upload a program, provided by Vigil, into the Citadel that would temporarily prevent Sovereign from opening the Relay.
Sovereign was able to take control of Saren's body through the use of his cybernetic implants. He used Saren's body to attack Shepard whilst also attacking the Alliance Fifth Fleet. After Shepard defeated the Saren avatar, Sovereign lost its shields, allowing the Fifth fleet to cause major damage to the Reaper's exterior. The final shot from the SSV Normandy brought about Sovereign's destruction.
Shepard realized that Sovereign was only a Vanguard, and that the entire Reaper fleet was still waiting for their return.
 Mass Effect 2
Legion reveals that Sovereign's true name is Nazara, with Sovereign being the name given to it by Saren. Legion explains that Sovereign had been in search of allies for the past 1000 years, eventually seeking the help of the Geth. The majority of the Geth, the "True" Geth, rejected Sovereign's offer of technology in exchange for their loyalty. However, some Geth accepted this offer, and were branded "Heretics".
After Sovereign was destroyed, debris fell upon the Wards. Due to reliefs efforts and the Keepers' intervention, little of Sovereign's technology could be retried for study. However, Turian scientists were able to replicate Sovereign's main weapon into a smaller, compact version for use on verious Turian ships. This weapon used an electromagnetic field to fire a stream of molten metal at the speed of light, and was named the Thanix Cannon.
Cerberus were able to recover enough technology to create EDI, an AI that could use anti-Reaper algorithms.
However, whatever remained of Sovereign was not enough to convince the Council of the existence of the Reapers. Instead they deemed that Sovereign was of Geth origin.