The Mu Relay is a mass relay located in the former Y;vak system of the Teestez Yu Nebula. Originally located in the Y;vak system, the relay remained in the system when it went supernova in 1817 BCE, although it was shrouded in hot dust and radiation that made it difficult to find for millenia. The relay remained lost until its discovery by the rachni in 193 BCE, found in what was once known as rachni space. It is known as the only relay capable of linking to the Refuge relay.