Substance

Substance was a sizeable Gas Giant that didn't really do anything except provide Installation 05 with something to orbit around. Installation 05 was put there as a failsafe protocol, so that if the Ring was ever compromised completely or if the superstructure gave way and the ring fell apart, the majority of its wreckage would be pulled into Substance and destroyed. This didn't seem to work when the Flood took over the ring, however,