|The following information strictly refers to Strygon's First Contact War Universe and is therefore not canon to the FreeSpace Universe, nor is it related. Also, it may contain spoilers regarding First Contact War campaigns.|
Abyssals are a hypothetical alien race or civilization believed to possibly reside in The Abyss System. Due to the extremely dense ionization of the local nebula within the system, the existence of such a race could not be confirmed up until now, but due to the sparse amount of scouting done in that system, there is a strong possibility that it has simply not been found yet.
The reasons for this hypothesis initially started in 2300 when the system was first discovered. Irregular EM and radio patterns intercepted by probes in the system strongly pointed towards the existence of some kind of fleet or other object emitting what is almost certainly a radio message, as no stars or other natural object has ever been observed transmitting these kinds of signals.
It is also very well possible that this nebula may be the location where the lost Pioneer-class Exploration Ship "Hyperion I" during the launch of the Three Pioneers may have jumped, presumably losing engine power shortly afterwards. This alone already warrants further investigation, which is currently pending.