- "They call the Kyln the stomach of the prison system: No matter how good you are going in, you come out pretty freakin' bad!"
- ―Rocket Raccoon
The Kyln was an interstellar prison facility run by the Nova Corps to hold convicts. Its galactic coordinates are M20H 119919142+0185112.
Star-Lord, Gamora, Rocket Raccoon, and Groot, were imprisoned here after being captured by the Nova Corps on Xandar. Gamora informed the others that the Collector was her employer, not Ronan the Accuser, and the four agreed to split the payment for the Orb if they could escape. Drax the Destroyer wanted revenge on Ronan for the death of his family, so he attempted to kill Gamora; However, Quill convinced him that Ronan would come for her and that keeping her alive was a better option.
Rocket, Quill, Gamora, and Groot formed a plan to escape. He told each person what he needed; Gamora was to get a guard's armband and Quill said he would procure a fellow inmate's prosthetic leg. While Rocket was discussing the prison's power source, Groot, without warning, extended himself and pulled it out as Drax watched.
As Rocket had predicted, Groot's removal of the power source caused the Kyln to switch to emergency power. Quill and Gamora went to their self-appointed tasks. As Groot attempted to hold off the Kyln Hoverbots, Rocket came to his aid and, with a weapon given to him by Drax, Rocket, and group managed to hold them off.
Meanwhile, Gamora managed to extract a security band from one of the guards while Quill collected the other prisoner's prosthetic leg at the cost of 30,000 Units. With all the items needed, the group entered the watchtower. When Quill put the leg down, Rocket revealed it was just a cruel joke, much to Quill's anger. As the guards began to fire at the watchtower, Rocket, using the security band and a Quarnyx Battery, managed to shut off all the gravity outside the watchtower and use the Kyln Hoverbots to get the group out of the prison area.
As the group collected their belongings, Quill noticed the guard did not put his Walkman back and went to retrieve it, taking the Orb with him to make sure the others didn't leave without him. After retrieving it, Quill found his way back to the Milano and the group departed.
Not long after their escape, Ronan and his Sakaaran forces invaded the Kyln in their search for Gamora and the Orb. Many prisoners and guards were killed, and others were interrogated for information about Gamora's whereabouts. Nebula received word of an incoming Nova Corps fleet sent to retake the prison. To ensure that there was no chance of anyone at the prison informing the Nova Corps of his objective, Ronan ordered Nebula to 'cleanse' the place before they left, which presumably entailed killing all the remaining prisoners and guards.
- In the comics, the Kyln has served as a prison for criminals and miscreants from across the universe too powerful to be held elsewhere. Galactus used the Kyln to imprison the Proemial Gods.
- The color stripes on the Kyln inmates outfit represent the number and the type of crimes for what they have been convicted.
- The Kyln is laid out similarly to a panopticon a type of prison which contains a central watchtower which has a 360-degree viewing area allowing a single guard inside to potentially have a view of all prisoners at once.