Serpent Nebula

The star system that is home to the Citadel.

The mass relay was reactivated in 2190, about 3.5 years after the Reaper War, at which point it brought the Sol System, the Perseus Veil, and the Annos Basin into contact with the Athena Nebula, Apien Crest, Aethon Cluster, and Krogan DMZ.

Serpent Nebula

Mass Effect: After Armageddon Toushea