Humanity has discovered faster than light (FTL) travel and can now use huge technological wonders, Mass Relays, that create a wormhole allowing for travel over vast distances. Having only recently made contact with other alien species, humanity has many foes among these new races.

The Reapers, a race of sentient machines, tried to wipe out all organic life in the galaxy. Through the efforts of the Systems Alliance and all other Citadel member's fleets and Commander Shepard's efforts the Reapers were defeated, for now.

13 years later the Citadel's repairs are completed. Life has returned to normal. The Systems Alliance has temporarily stopped their expansion to protect the colonies they have. The tensions between species has lessened. The Geth have expanded their territories, claiming most of the Terminus System. There are more frequent Geth attacks now. The Quarians have begun to find an ally in the Citadel council. The Quarians now have representation. Trouble is brewing though. A new threat has appeared and this threat could cause an intersystem war.

The Geth are trying to eliminate the Quarians once and for all. The Geth have discovered the location of the Quarian Migrant Fleet. It is a race against time to stop the Geth. The Migrant Battles began. The Geth's first wave wiped out most of the Quarian's defenses. The Geth were on the verge of victory then the Turian Peacekeeper Fleet arrived as reinforcements for the Quarians and pushed back the Geth. The attack was stalled for now.

The son of Saren was discovered during this battle and he wants to continue his father's work. A new foe has arrived as well. The time of the Reapers is coming again.

The Geth's attack on the Migrant Fleet pushed the Citadel Council into mobilizing the Citadel fleets against the Geth. The Citadel fleets attacked the Geth homeworld. The battle raged on and many were killed. The Citadel Forces discovered the location of the Geth capital city, Judecca. They began to siege the city.

The leader of the Geth ended up being a Reaper named Fuhrer. The city also ended up being a massive Reaper. The battle came to an end when the capital ship of the Geth forces, Liberation another Reaper, was destroyed and the city fell. The Citadel Forces successfully defeated the Geth. The Geth retreated, the Reapers were stopped and the son of Saren was captured.

The galaxy is in a false peace now.

Quickly after the fall of Judecca, Yarik Streydus, who had been working with the Geth in the Skyllian Verge for 13 years, returned and was accepted as the leader of the Geth. Their forces have nearly recovered fully from Judecca, while the Council tries desperately to bolster their numbers.

The Son of Saren was tried and convicted of treason and sentenced to be executed by firing squad. A daring raid by Kaleb and Nero allowed him to escape.

3 colonies in the Terminus system have been subjugated by the Geth, and the Alliance has dispatched a small force to re-capture or destroy them.

While preparations for the attack on Elysium neared completion, Yarik Streydus, leader of the Geth, took one last vacation to the Citadel, believing himself safe in anonymity for the time- he was attacked by members of the STO the first night there.

The members of the STO escaped with an OSD containing information about the invasion, mainly where it would take place. The Alliance, the only orginisation to which the STO answers, began diverting forces to Elysium immediately.

After a devastating loss at Elysium, Alliance forces have devoted more troops to protecting the borders of space. Many Alliance soldiers are disappointed with the Council, who refused to send aid to Elysium due to their own reduced forces.

The Geth, meanwhile, have already moved on from Elysium and are preparing to attack New Eden, one of the Alliance's bigger colonies, largely considered by the Geth as a representative of human gluttony and luxury.

The Geth fleet attacked the Alliance colony of New Eden and managed to capture it with few losses in space. On the ground, the Alliance forces, while devestated by the end of the battle, had taken on average 10 Geth for every man.

On the Citadel, after having rescued councilor Khearkas from a human kidnapper with unknown motives, Commander John Shepard refused a medal awarded to him by the council, stating he would not accept it until Khearkas personally thanked him. Shortly thereafter, Khearkas collapsed, believed to be a panic attack due to the large amounts of stress he's suffered recently.

Commander Shepard's actions, as well as the Council's refusal to send an entire fleet to New Eden, further widened the apparent rift between the Alliance and Council. Another rift, within the Alliance itself, has appeared, as Admiral Bauer of the Alliance navy was killed after attempting to murder Admiral Hackett. Lt. Commander Donald Cochran, one of Bauer's subordinates, is now on the run from the Alliance with the SSV Davenport, his ship before he was discharged.

After a devastating assassination attempt, leaving both the Asari and Salarian Councilors dead and the Turian Councilor in temporary charge of all Council affairs. An imposter posing as Richard Crawford was seen emerging from the crowd before shooting the Councilor and Executor Cyrus of C-Sec.

In a shoot-out between a joint squad of C-Sec agents and Terra Firma guards, the headquarters of the STO, an alliance-funded group of assassins, was wiped clean and the STO has been dissolved. No evidence of their ties to the Alliance has been found, though they are heavily implied because of the organization's location on the Citadel itself.

After the destruction of the STO the Citadel Council began to crack down on all other illegal special forces groups.

Terra Firma, a strong political party in the System's Alliance, began protesting against the Council. They were against anyone that wasn't human. The protests broke out into riots and the entire glaxy was plunged into turmoil. Terra Firma gained enough support and power to pose a threat to the Alliance. The Alliance Civil War began.

After Dygnitas Sentrus saved Yarik Streydus from an assasination attempt the two joined forces and began to plan their assault on the Citadel. They combined the Geth Armada with Dygnitas' Dignified Forces and began to head to the Citadel.

In the mean time a rogue geth named Sythenus was able to seek the help of the Council. He requested a small team to find a cure for indoctrination in order to free the geth from the reaper's control. Kaleb Sentrus was made leader of this mission and a small and diverse team was assembled.

The Geth Forces finally made their attack on the Citadel. Due to the Civil War going on the Geth were able to attack the Citadel at its weakest. After hours of fighting they broke through the Citadel Fleet and began to land forces on the Citadel. The Geth successfully closed the arms and blocked off the Citadel Fleet. The forces in the Citadel were isolated.

The team that was searching for the cure to indoctrination finally found out what the cure was, dragon's teeth. The team went to a prothean planet called Haven and encountered a large amount of geth and husks already there. The team was able to breakthrough the overwhelming odds and they were able to get the cure. Now they needed to use the cure.

A prominent turian clan called Segonashi betrayed Dygnitas and were able to temporarily disable the geth and get any survivors out of the Citadel. Shepard and his team then infiltrated the Citadel and were able to get to the Citadel Tower. Yarik Streydus finally realized that what he was doing was wrong so he deactivated the geth around the Citadel to give the Citadel Forces a chance to stop him. Dygnitas realized that Yarik betrayed him so he escaped through all the confusion. John Shepard and his team were able to open the arms and the Citadel Forces took back the Citadel. Yarik Streydus was supposedly killed and Dygnitas Sentrus disappeared, but their followers were captured.

The team with the cure made it back to the Citadel and administered the cure to the geth remaining at the Citadel. This small faction of cured geth were allowed to go back to the Terminus System and begin life anew.

The Alliance Civil War was becoming more and more violent while time passed. Terra Firma was able to take control of the inner colonies in the Sol system and were holding their ground. Other forces that helped in the Battle for the Citadel assisted the Alliance.

The Alliance made a massive counterattack. They began to siege the inner colonies. After months of fighting the two sides agreed to a cease fire. Terra Firma lost much power, but were still able to maintain their status as a dominant political party. The Alliance took control again. All the leaders of Terra Firma were arrested and order was maintained.

For the past two years there has been peace. The galaxy has been rebuilding itself from all the constant war. The Systems Alliance is completely stable and the humans have finally been given a seat in the Council.

The Citadel has been fully repaired as well as its fleets. New organizations have been established to maintain peace. The Segonashi and Liandri along with countless other groups have been recognized for their bravery during the Citadel Wars and Alliance Civil War. Geth activity has increased, but the Citadel forces are far superior. The Batarians have gotten more violent and agressive against the humans.