Lobo hardly needed to explain. Takron-Galtos was known to virtually every Justice League member; that planet was infamous in any universe.
You could call it a prison, but in essence, it was more like a Concentration Camp. Built by the Little Blue Men, the Guardians of the Universe, it was managed by specially appointed personnel and designed specifically to hold "high-security" criminals from across the Milky Way Galaxy.
This famous prison planet was slightly larger than Jupiter. It had been urbanized from the inside out and held a total population of more than thirty billion, almost all of them prisoners confined in cells resembling capsule hotels.
It had been established thirty thousand years ago. The Green Lantern Corps officially called it a "criminal rehabilitation facility," while Hal was more realistic—he called it the "Black Prison."
The entire planet was managed by a single branch of the Science Police. The Science Police were future Earthlings from the year 2976, freaks from some unknown Timeline. They pursued absolute order through the eradication of emotion, embodied the merciless ideology of future Metropolis, and even regarded eliminating the Justice League as their duty.
Other than those police, Takron had no guards at all. The entire planet was controlled by machinery and quantum computing hubs, with every aspect of every prisoner's life regulated to the absolute limit.
For instance, even using the toilet there meant being monitored by more than a dozen devices. Then the deranged computers analyzed everyone's feces to ensure they had no suicidal tendencies and could remain imprisoned until the very end of their natural lifespan.
So how did the Green Lanterns define "high-security" criminals when making arrests?
A little delinquent like Harley, carrying more than seven hundred murder charges, was nowhere near qualified to stay on Takron. To catch the attention