The Rachni continue to be a problem in Mass Effect 3 Legendary Edition. You initially encountered the last Rachni Queen in the first game, and you could free her or let her die.
That decision matters the second time you meet the Rachni Queen after you discover she’s been captured by the Reapers and forced her to breed an army for them. After you’ve saved Krogan’s only fertile female from the Salarians, the leader of Krogan asks you to find their missing scouts that went after the Rachni. If Grunt survived the suicide mission in Mass Effect 2, he would lead Aralakh Company. When you reach the end of the mission, you have a choice to save the queen or let her die.
Should you help the Rachni Queen escape or leave her?
The choice to let the Rachni Queen live or die is based on whether you let her live or die in Mass Effect 1. If you allow the Rachni Queen escape from Noveria, she will remember that you helped her, and when you let her escape, she becomes a war asset worth 100 points. However, even if you killed the Rachni Queen on Noveria, the Reapers will have created one, and you have the same choice, and you want to make sure to leave this queen.
The big difference between the two is the aftereffects. The Rachni Queen that you let live in Mass Effect remains an asset for you. The Rachni Queen that the Reapers created will initially become a war asset worth 100 points, but she eventually turns on you, harming part of your war assets. She destroys Aralakh Company and 100 points worth of your Alliance Engineering. You only want to let the Rachni Queen die when you initially killed her in the first Mass Effect.
It’s important to note that regardless of what Rachni Queen is during this mission, if you let her escape, Aralakh Company will remain behind to help her leave, dying in the process. Aralakh Company will live, becoming a war asset worth 25 points. However, if Grunt is on the mission, he will survive unless you do not complete his loyalty mission from Mass Effect 2. He becomes a war asset at the end of the mission, worth 25 points.
This is one of the important decisions you can make in Mass Effect 3. Although it doesn’t have huge ramifications in your story, or the ending, it can provide substantial assistance to you to bring up your War Score. It’s one of my favorite missions because it ties a major mission from the first game with the third one, and you only had small story ripples of what the Rachni Queen was doing in Mass Effect 2, but only if you let her live.
It’s a better choice to help the Rachni Queen escape the reaper nest, but only if you let the one on Noveria leave. Leave her and go to the caves with Aralakh company if you did not.