The Internment Zones

After the Great Titan War, most Eldians who were stranded on the continental mainland were left at the mercy of an unforgiving Marleyan nation, which was nevertheless aware of the military potential of their genetic trait. To exploit it, the Eldians were segregated from the rest of the population into designated areas such as the Liberio internment zone under the watch of the Public Security Authorities. These ghettos act as a reserve pool for Pure Titans. In wartime, internees were brought out to be turned into Titans and released onto battlefields as living weapons.
To justify its exploitation, Marley indoctrinated both its citizens and Eldians with a revised history which demonized the latter group. As a result, the Marleyan populace saw the Subjects of Ymir as evil due to their ancestor Ymir Fritz's deal with the "Devil of All Earth."On the other hand, average continental Eldians, such as Yeager and Gabi Braun, became convinced that they were genuinely indebted to their "merciful" Marleyan overlords, and that the only ways to redeem themselves would be through loyal service to the Marley Motherland and the extermination of "bad" Eldians on Paradis Island.
Compared to the Marleyan society beyond the fence, life inside the internment zones is lackluster but not poverty-ridden. For example, the Yeager family was able to make a living working as doctors, a reputable profession; and the residents were able to put up a feast for their family members returning from war. Nevertheless, they do have to endure abuse from PSA guards from time to time, which are occasionally lethal, as evidenced by the murder of Faye Yeager. Movement in and out of the ghettos are also restricted, with the camp's main gate only open at a specified time of the day or during special occasions, such as the gathering to welcome the troops home. One has to produce a permit in order to gain passage.
Not all Eldians suffered that fate, however. A few Eldians were awarded "honorary Marleyan" titles for services to the Marley Motherland, such as the Warrior Unit and their families. With this status, Reiner Braun claimed he could live outside of the internment zones if he wanted to and asked for permission.
By the year 832, the military value of Eldians was put into question. It was known that Pure Titans are inherently uncontrollable and pose as much a risk to the enemy as to itself. There were opinions for the extermination of all Eldians in Marley. At the time, Eren Kruger noted that once Marley secures the Founding Titan, the debate would end in favor of those opinions and seal the doom of all Eldians.
By the year 854, however, the attitude changed again. The Marley Mid-East War laid bare the fact that Titans are losing to the advancing military technology deployed by Marley's many enemies, but since the nation needs time to close the gap in arms development with the rest of the world, the Eldians are still needed as a stop-gap measure. It not only prompted the Marleyan leadership to renew the operation to seize the Founding Titan, but also started a "symbiosis" relationship between the two ethnic groups where the Marleyans need the Eldians to sustain its military might and the Eldians need Marley to keep a hostile world at bay. After the war, Eldians are not only hated in Marley but also all around the world, due to the usage of Titans by Marley in wars of expansion, much like during the age of the Eldian Empire. The universal hatred escalates to the point that most of the world nations now demand the extermination of all Eldians but the Tybur family.
The Marleyan government determines the ethnicity of its citizens with blood tests, and the result of which affects their eligibility to get into privileged professions. To join the Public Security Authorities, for example, one has to prove that they are not of Eldian ancestry by passing the test. Despite that, agents of the Eldian Restorationists were able to get around it by using falsified medical records and having their tests done by doctors sympathetic to their cause.
Although harsh, it is noted by Udo, who used to live in a different country, that Marley is, in fact, more tolerant of Eldians than many other countries, wherein Eldians face much severer hostilities that make the Marleyan discrimination pale in comparison. There are some Marleyans, such as Theo Magath or the guards that Gabi Braun befriended, that genuinely care about the well-being of the Eldians under their care. Additionally, the Marleyans in the Panzer Unit have a friendly relationship with Pieck.[56] There exist several organizations in Marley who fight for the Eldian people's human rights, but they face hostile critics from the general population for taking defense of the Eldians.