The Van Graff Rift
Initially discovered by the SAS Constitution in 3514, the Rift was named for the science officer on duty that first noticed the subtle abnormalities in space near the vessel. From the outside, the rift appears to be a relatively normal patch of space in the void between solar systems, baring some unusual micro-fluctuations in gravity and radiation.
Entering the rift, however, is nearly akin to stepping into another universe. The outermost “shell” of the Rift is like a light-years wide stealth shield of some sort, hiding the contents of the Rift from outside observation.
Within, the physical laws of the universe begin to break down. Points in space light years apart are connected seemingly at random, hollow planets orbit black holes without being drawn in, and anti-matter exists without the volatile reactions it would normally have with regular matter.
All attempts at explaining the cause of the Rift have been equally confounded, and no solid answer has ever been accepted. The most popular theory, perhaps popular because it can NOT actually be confirmed, is that the Rift represents the “cosmic laboratory” of an ancient alien species, though what they were attempting to accomplish, and whether or not they succeeded, may never be known.
Given nothing else like the Rift has been discovered elsewhere in the galaxy, the likelihood of it being a naturally occurring phenomena seems low. Whatever species may have created it, no other trace of civilization has been discovered within any of the nearby solar systems.
Incident Report UE.67012.e423
Occurring in 3891, this obscure report was obtained and leaked by an unknown agency over a century later, and became especially widespread in the early days of the Judgment War, which began in 4006.
The report contains communication and sensor logs of a fleet of approximately thirty Solar Alliance vessels undergoing a long-range patrol in the Onias Sector. All activity was effectively normal until a surge of a previously-unknown kind of energy was detected. Visual reports claim seeing a brightly-burning light near the ships, from which extended gaseous tendrils towards the vessels at tremendous speeds. Ships caught within the tendrils reported powerful gravitational forces, rocking them violently, before all communication would suddenly be cut off, and the ships would effectively vanish without a trace.
Fearing for their safety, the remaining ships engaged emergency foldspace jumps, hurling them several light years away almost instantly. However, the unknown light quickly appeared again, and several more ships were drawn into its tendrils, leaving the remaining vessels to flee. Any attempts at attacking the light seemed to have no effect.
This process repeated, with emergency broadcasts being sent, until all thirty vessels had vanished. A force was dispatched to investigate, but found no trace of either the ships nor the unknown light. Despite this, the area was quarantined until well after the Judgment War was underway.
What caused the report to become popularized after the outbreak of the Judgment War were theories that the mysterious light and gaseous tendrils was some sort of “scouting move” by the Great Enemy; its first ventures into our reality from their own, seeking to assess the capabilities of the Solar Alliance before a proper invasion.
This theory is widely discredited, however, as it was never repeated by the Great Enemy, and the energy signatures of the light do not match anything ever used by them. It is generally accepted that the method of attack used by the light displayed signs of sentience, but no one has been able to conclusively prove the source of that sentience.