Dark Nebula

Throughout known space there are areas, often tens of parsecs across known as Dark Nebulae. These represent accretions of gravitic anomalies and higher than typical densities of dust, proto-stellar matter and dark matter.
Whilst it is still possible to transit Dark Nebulae through hyperspace, there is a small but measurable probability of a drive failure due to gravitic eddies.

Systems located within dark nebulae are sometimes colonised, even given this risk.

During the First Exterminator War it was theorised that the new enemy might have somehow originated in dark nebulae. This theory was quickly disproved.

Dark nebulae are also sometimes the location of dangerous spacial anomalies, which are, fortunately extremely rare, hard to detect and nowhere near systems of interest to humanity and therefore regarded as a negligible risk to navigation.

An untethered dimensional rift was discovered in the Dark Nebula of Quadrant 7, which is thought to be a portal to another universe, provisionally named Universe N.