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 the last part we saved a krogan female ,,Eve'' and started working on curing the Genophage(a biological weapon created by salarians and deployed against the krogans by the turians. It made most krogans infertile). We also met our friend Mordin. Wrex and turian leader asked us to do a few favors for them. After that we gave crime boss Aria control of three mercenary groups.
In this part we met with Aralakh company of krogans and their leader our good friend Grunt. They were investigating a possible appearance of Rachni(insect-like species). Grunt was glad that we helped him in his right of passage in second game. That allowed him to become a leader of the strongest krogan unit under Wrex control. His krogan blood demanded to fight a old enemy(Rachni).Javik had not met Grunt before but immediately recognized him as a strong warrior. After that we went into a building and it collapsed. Then we found and confirmed that Rachni were there. Also they become even more dangerous than in the past because they were turned to Reaper minions. One thing I really like about this game is variety of enemies. While fighting the Rechni Grunt said a cool line about ammo. After that we found Rechni Queen that was enslaved by Reapers. We spoke and it promised to support us if we will spare it and set it free. We agreed. This meant that krogans had to hold of Rechni while the Queen escapes. It seemed that Grunt is also making a last stand but he was able to beat a wave of enemies and survived to tell the tale.
After that we met with lieutenant Victus and his turian crew. His men were no longer trusting him because of the heavy loses their had suffered. Victus told us about his mission- apparently on krogan homeworld is an enormous bomb. Victus had to disarm it but not it is at the hands of Cerberus. We forced Victus to continue his mission and kick his men asses till they will fall back in line. Later Victus revealed that bomb was originally placed not by Cerberus but by turians hundreds of years ago. When we reached a bomb Victus found out that Cerberus installed a firewall so we had to defend him while Victus was trying to bypass it. After he bypassed the firewall the bomb activated so Victus sacrificed himself in order to disarm it. It is a shame that turian secrets costed Victus and his men's lives but it was still better than what would had happened had the bomb exploded. That explosion would have meant all out war between turian and krogan and entire galaxy would be harvested by the Reapers.