Noveria

Anoleis.

Shepard arrives at Noveria and discovers that Matriarch Benezia recently arrived. She and Saren are investors in Binary Helix, which has a lab up on Peak 15. Benezia has gone there on business. However the lab has since issued a Code Omega signal, meaning there are critical problems, and a blizzard has cut off shuttle access. After wrangling with Administrator Anoleis, Shepard, along with Liara and Garrus, manage to get a garage pass and drive up to Peak 15.

Matriarch Benezia.

The facility is deserted save for geth and bizarre creatures —the rachni—which have escaped from the labs. The rachni were hunted to total extinction by the krogan more than a century ago. These rachni are the first to be seen since then. Shepard reactivates the station's VI, Mira, and goes up to Rift Station looking for Benezia. Rift Station is full of science staff sheltering from the rachni attack; Shepard can help them out but gets attacked by those loyal to Benezia. The squad finds out Binary Helix discovered a long-frozen rachni egg that turned out to be a queen, and were trying to breed an army from her brood until the rachni turned on them.

Rachni Queen.

Down in the labs through the maintenance area, Shepard finds Benezia with the Rachni Queen. The matriarch attacks the squad, but after a fierce battle Benezia manages to overcome the indoctrination that Saren has used to control her, and tells Shepard the truth. Saren wants the location of the lost Mu Relay, and sent her to retrieve it from the queen's genetic memory. Benezia doesn't know what else he is planning. She hands the coordinates over to Shepard, but becomes lost to the indoctrination again and the commander has to kill her.
He is now left with a decision on what to do about the rachni, whose ancestors were purged for their savagery. Shepard interrogates the Queen to gain incite into her character. The Queen insists that she only wishes to restore her species' population, and promises to raise her young in harmony. After deciding to release the Rachni Queen into space, Shepard leaves Noveria with Benezia's data and another piece of the puzzle, and heads for the planet Feros.