In this game our main mission is to unite humanity and aliens of the galaxy in order to stop the reapers( godlike machines that come every 50000 years and wipe out all intelligent civilizations.)
In last part we met quarians admirals who were fighting against Geth(intelligent robots). They told us that Geth are being improved by Reaper code and are destroying the quarians. We found that the reapers were using our friend Geth Legion to transmit the signal to other Geth and control them. Fe freed Legion. After that we escaped. After that our other friends wanted to know if we can really trust Legion. Our former crewmate Miranda asked us to give her some information.
In this part we had to disable some giant guns and destroy a jamming tower so we could contact a quarian admiral. He wanted us to save his men instead but we decided to save the admiral. He is more sensible than his peers and didn't wanted war with the Geth. So we thought that someone like this could be useful for us to end the war.
After that we spoke with our friend Legion and he invited us to Geth consensus. We traveled into Geth virtual reality. Legion pragramed it to look familiar to us. Still it looked like a bunch of blocks made of cubes. We had to destroy Reaper infected data. After that we saw a few important fragments of Geth memories. We saw how quarians created Geth. Geth were too smart. And at some point asked their creators a question- Does this unit have a soul? After that quarians panicked and attacked the Geth. Geth wanted to survive and fought back. We destroyed Reaper infection and returned to real world. After that we found out that some of Geth decided to join us.
Then we did a main mission in the quarians Homeworld. Legion told us his secret- He still has Reaper code and now can hack any Geth. It promised to get us an escape vehicle. After a while we met again. Ans saw a Reaper on Rannoch(quarians Homeworld). We could have escaped with Legions help but then Reaper would have continued to control Geth and destroy quarians. So we decided to destroy it here and now. We signaled our ship Normandy and quarian fleet the precise location of the Reaper. They bombarded it multiple times and finally managed to bring the bastard down. The Reaper recognized us and spent his last minutes threatening us and saying some weird BS like,,You represent chaos, we represent order'' and ,,we are your salvation''. We told it that we are not afraid and that we will bring destruction upon the Reapers. After that we finished him off. After that quarians went nuts again and wanted to destroy all remaining Geth. Legion asked if Geth deserve death. We said no. So it began uploading Reaper code to all the Geth. After death of Reaper this meant that Geth will become a true intelligence. Quarians still wanted to destroy Geth but we told them to sit the hell down otherwise they will regret it. Quarians finally listened to reason and stopped attacking the Geth. Legion told us that the code is insufficient. After that Legion sacrificed himself in order to turn Geth into a true intelligence. After that Geth and quarians achieved peace.
We returned to the Normandy. We got a call from Asari Councilor. She wanted to discuss something in person so she invited us to the Citadel. After that we talked with Admiral Hackett and asked why he believes that we are the right person for all this saving the galaxy thing. After that we spoke with EDI. And she told us that before death Legion started calling himself as ,,I'' instead of ,,We''. In other words he became a true person.