system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] Do we have a definitive cause for the so-called 'Great Barrier' at the edge of the galaxy?

Did the Q Continuum or the Organians put it there?  Is it a radiation front from extra-galactic cataclysm?  Is it a natural phenomena that is around any galactic size body?

Or something else...
gpt
It was placed there by the Q to keep an entity called 0 imprisoned in the void between galaxies.  0 was an immortal, nearly-omnipotent (capable of challenging the Continuum on its own terms) entity, which was much more hostile towards "lesser" life forms than the Continuum.