The Invid Sensor Nebula were an interstellar, migrant gaseous cloud that roamed the known universe in search for where the Flower of Life has taken root. They also served as the Invid Regess' eyes and ears, able to communicate via or fourth dimensional communication/data transmission through the stars, relaying valuable information for the Invid. Once a world was found where certain condition were met, the cloud would transmit the data to the Invid. It then acts as a hyperspace beacon for the approaching swarm.
According to scientists of the Robotech Expeditionary Force (REF), what made the Invid Sensor Nebula unique was the fact that it was self-illuminating, with numerous small “proto-stars” (which should be impossible). Research drones also determined the presence of organic matter within the Nebula itself that acted as some form of intelligence, capable of responding to stimuli. These discoveries proved to Terran scientists just how little an understanding of Robotechnology they had unraveled since its discovery at the turn of the millenium.
It was believed that the Nebula present during the Second Robotech War was but one of a series of sensor nebulas that the Invid employed throughout the cosmos. One popular theory on how quickly Earth fell from the initial invasion of the Invid Regess was that the Invid Sensor Nebula mapped the entire planet out of concentrations of protoculture and protoculture activity. The nebula possibly used hyperspace or a fourth dimensional communication/data transmission to contact its masters once it detected the release of the Invid Flower of Life.
Some time during the Second Robotech War, the Nebula was drawn to Earth due to its unusually high readings of protoculture. The Nebula waited, and kept a close watch at the emerging conflict between the United Earth Forces and the Robotech Masters. After the Flower of Life was released, thanks to a miscalculation by the late Zor Prime, the Nebula signaled the Invid Regess to proceed with a full fledged invasion on Earth. The Nebula awaited the arrival of the Invid swarm, before moving on in search of other sources of protoculture.
During the Invid Invasion, the Sensor Nebula moved elsewhere in the universe. It was believed, based on statements made by the Invid Regess, that the sensor nebula may have detected another world supporting the Flower of Life. This world was possibly where the Invid migrated to after the end of the Final Battle of Reflex Point.