Inter-Dimensional Fatigue
Dimensional fatigue — also Inter-Dimensional Fatigue, or (I)DF — is a catchall term for processes or forces that weaken the boundaries between "dimensions" or space-times, allowing information or objects to pass from one to the other. The form of DF most familiar to the races of the Alliance is the QuasiSpace Portal Spawner, used to access QuasiSpace from HyperSpace.
The only race known to be familiar with DF is the Arilou La'leelay, who provided the Portal Spawner for Alliance use during the war but otherwise strongly discourages DF research as incredibly dangerous. The last known race to have attempted such research, the Androsynth, were destroyed utterly as a result. What records exist seem to indicate that acquiring knowledge such as images and other information obtained through experimental DF technology somehow made the Androsynth's minds visible to beings that exist in other dimensions. This led to a series of spontaneous DF events generated by those entities such as anomalous regions of high gravity ("mosquito mange"), spontaneously generated forces ("poltergeists") and sensory manifestations ("ghosts"), which in the end were somehow responsible for the race's disappearance and replacement by the Orz. The Arilou claim to have protected at least the race of Humans from a similar fate by unknown measures, but warn that any increased knowledge among Humans of DF phenomena would create similar vulnerabilities. Apparently the fate of the Androsynth was not unique; the Arilou claim that a DF event was also responsible for the disappearance of the star Alpha Corvi and its planetary system.