Research into psionics and psionic life accidentally goes too far, creating a psionic virus.
* Being non-corporeal, the virus (or germ, or worm) can transmit across vacuum. Ship crews can therefore carry and transmit the disease. Allowing the presence of infected ships in your systems is not recommended.
* Default solution is "kill it before it can infect you" and "purge the infected".
* Robots are immune. AI research and extensive use of robotics is therefore a good idea to fight this threat.
* Materialists may be especially susceptible because of their disbelief in non-material things, as they typically do think the thought "I must not allow demons to influence me" and therefore have not practiced their "psionic immune system".
Such a psionic virus could potentially be used to explain a "zombie apocalypse", or the creation of an "Overmind" that seeks galactic domination.