Line Installation 1-4 served as a Flood research facility and a defensive installation. It possessed a powerful energy weapon system that was capable of shooting down any ships passing nearby, even when in Slipspace, causing them to crash down on the moon. The Installation had its own Monitor named 686 Ebullient Prism which had a sizeable force of Sentinel and special Gatherer units under its command. The Installation itself is a vast underground complex with tunnels and hallways reaching kilometers deep. Most of the tunnels appear as if they had been designed with flying machines such as Sentinels in mind, as vertical or angled service tunnels are more frequent than walkways.