Conversion centers are facilities widely used by the Chimera to speed up the process of converting Chimeran Virus-infected humans and possibly other creatures into Chimera. Conversion centers are equipped to handle possibly hundreds of soon-to-be Chimera.
The interior of a center is very much like an assembly line, with the newly created Chimera rapidly churned out. Infected victims are brought in by Carriers while any uninfected prisoners are kept in makeshift pens until Crawlers are dropped in to infect them. They are then given surgical implants, and placed into a network of tubes where the bodies undergo different stages of conversion. They are then wrapped in cocoons to accelerate the transformation and turn into a different Chimeran creature depending on the strain of the virus. In the birthing chamber, the cocoons are opened and new creatures are born. In the case of Hybrids and most other Chimera, it is here that they forcefully and surgically attached with cooling units.
Following the failed aftermath of Operation Deliverance, the U.S. 1st Ranger Regiment were decimated from falling victims to Spire missiles and were transferred to the Grimsby conversion center, where Captain Rachel Parker was also imprisoned. Nathan Hale, though infected and semi-immune to the Chimeran Virus, was among those who were taken and managed to rescue Parker before escaping.
By the time of the Battle of London and the decimation of the Chimeran forces on British soil, it can be very likely that the conversion centers throughout the United Kingdom fell into disuse.
Tom Riley and Ellie Martinez rode a Carrier to the Conversion Tower in Appalachian Mountain, hoping of rescuing any survivors, including Tom's family, and as well stopping Richard Gorrell's plans. Tom, however, was forced to euthanize Natalie, who already been infected and beyond rescue. Ellie managed to rescue Rachel Riley and a large group of uninfected survivors.
Tom tracked down Gorrell, who then attempted to gain control over an unfinished Leviathan. After failing to manipulate it, Gorrell fled and forcing Tom to battle the Leviathan. The battle destabilized the facility's power reactor core, causing the unstable chain reaction which led to facility's destruction before Tom escaped
Following the Battle of London, conversion centers are still used by the Chimera. Yet the original centers are found abandoned and in the process of being dismantled by Chimeran Drones. It is theorized that the raw materials taken from the old conversion centers are being taken to the new ones in Chimeran Towers across Europe. It is in these new conversion centers that the Boilers and Hags are being created as part of this new conversion process. The one in Bonn appears to have been made a long time ago and appears to utilize water from the Rhine River in order to function, and turning the river into a dry bed in the process. However, the Bonn conversion facility was destroyed by James Grayson.
The Chrysalis Lair was one of these new conversion centers and a central hub for Carriers. During the final battle of Operation Overstrike, James Grayson infiltrated the "heart" of the Chrysalis Lair and injected Claude Bouchard's serum, allowing the contaminated fluid to be transferred from the Lair to all conversion facilities in Western Europe, grounding the conversion process to a halt and killing the Carrier strain - although temporarily prior to the Chimera's creation of the Spinner strain.
By the events of Resistance 2, the Chimera did not need the conversion centers as much as before, with the new Spinner strains in creating new creatures more rapidly and quickly. Conversion centers were still used for advanced strains, but not used as much due to body shortages and the Carrier strain dying off. One such conversion center is seen in the Holar Tower and is also mentioned that the Chimera still use makeshift conversion centers in Resistance: The Gathering Storm.
By 1957, the Chimera have completely abandoned their use of conversion centers, since all human survivors were inoculated with the Hale Vaccine which becomes immune to the Chimeran Virus. The Chimera has given their new genocidal intentions in wiping out any remaining humans rather than capturing and infecting them.