Unearthly, glowing shapes float smoothly through the walls of the station. Everyone present sees them, yet they never appear on images or footage. Their drifting is almost random, but they drift closer and closer to brains and cyberbrains. If allowed to come close enough, they will fly into a head and curl up inside.
Wisps seem to exists only in the minds of those who perceive them, suggesting they are hallucinations, yet their forms and locations are consistent between multiple viewers, suggesting some degree of reality. The exact nature of ghosts has proven difficult to pin down. The leading hypothesis is that they are a form of asynch mind-attack, but the examination of victims has been unable to find any of the usual traces of aggressive memetics. The other hypothesis is that they represent some new form matter, but this has been impossible to substantiate.
Every wisp is unique in appearance. Generally, however, they resemble the translucent, glowing skeletons or exoskeletons of alien beings.
Wisps do not interact with matter, and can pass at will through any barrier. Their slow speed and roundabout movement pattern means they approach characters with an effective speed of 1/10.
If a wisp enters a characters head they suffer no apparent ill effects, but the wisp "marks" them for exsurgents. Exsurgents will not attack that character unless attacked first, but will attempt to infect them with their strain of the virus.