Attican Traverse: Krogan Team

Acquisition
The mission is acquired automatically after completing Priority: Sur'Kesh.

Walkthrough
After you rescued the krogan female Eve, Urdnot Wrex or Urdnot Wreav asks a "big favor" of you. A krogan scouting team has gone missing while investigating rumors of activity at the rachni relay. He asks you to investigate.

Upon investigation you will meet up with Aralakh Company, led by Grunt (or Urdnot Dagg if Grunt did not survive the Suicide Mission) and proceed through the tunnels in search of the Central Chamber. Be sure to check the hollows for ammunition, M-451 Firestorms, and a dead krogan scout that will make Citadel: Krogan Dying Message available, though it will not appear in your Journal. (Ereba is located in the Presidium Commons, behind the counter of one of the shops.)

You will have to fight your way through two caverns with several Husks, Cannibals, and Ravagers. During the trip through the underground tunnels and some of the encounters you will come across Spore Pods and Gestation Pods, both of which can damage your shields if you are not careful. You will come to an overlook where you will see Aralakh Company holding off Reaper forces. Proceed down the overlook and disable the Reaper Node. The Reaper forces will retreat and Grunt/Dagg will tell you that Aralakh Company will stay back to hold the position and give you time to "finish this." Proceed through the Narrow Passage to enter the Central Chamber.

Reaper fortifications will then extend upward out of the ground and encase you on the walkway. To bypass the walls, you must disable a Reaper node up and to the left of the forward fortification. The left wall will retract once disabled, so be prepared to fight the waiting Reaper forces. Once they have been defeated, proceed toward their position and disable a second Reaper node, retracting the barriers on the right side of the walkway. Double back and exterminate the Reaper forces before disabling the third and final Reaper node. Fight against one last wave of Reaper forces, and once they have been defeated a cutscene will commence. You will talk with the Breeder, an indoctrinated rachni queen and be given a choice: Leave her or help her survive.

Outcome
If you leave the rachni queen to die, you will gain Aralakh Company as a war asset worth 75 points, but no rachni assets due to their xenocide and/or enslavement by the Reapers. (Abandoning the rachni queen will not halt the Reapers' supply of Ravagers.)

If you choose to rescue the rachni queen, Aralakh Company will suffer grievous losses in the holding action, reducing their strength to 50 points. However, rachni workers worth 100 points will also join the effort.

No matter what you chose with the rachni queen, Grunt/Dagg will sacrifice himself so that that you can make it to your shuttle no matter which choice you make. However, if you completed Grunt's loyalty mission (Grunt: Rite of Passage) in the previous game, he will survive the heroic sacrifice and return as a war asset (25).

If the rachni queen was killed in Mass Effect 1, then in Mass Effect 3 the Reapers will construct an artificial queen so they can have a rachni army to turn into Ravagers. If Shepard chooses to free this queen, then unlike the queen from Noveria, this artificial queen eventually proves untrustworthy after a few missions, taking away the rachni workers war asset she gave at first and sharply reducing the Alliance Engineering Corps.