Given that the Plazma Burst series, canonically, is mostly Correction Nine's fault, there should be expansive lore about them. Surprisingly(or maybe not), their quite limited lore is the most detailed canon in the series. Techswordninja's timeline gives an outline that I recommend reading before continuing.
We know C9 opened the portal to the Ursurpation homeworld around 25 years ago, and sent (at the very least) the Marine and Noir Lime back in time to prevent this from happening. Shortly after, the group was dissolved and its equipment was sold to various factions.
This brings me to the reason I made this post-Why was C9 dissolved, and what took place in this era? I'll let you guys discuss it before I put my quarter in.