Case 53s, known to Cauldron as Deviants or Subjects, were amnesiac parahumans, usually with severe physical alterations, branded with a "C". They were so-called because their origin was the 53rd anomalous case investigated by the PRT.
Case 53s were found in out of the way locations in urban areas across North America and around the world. They all had retrograde amnesia, with their first memories being waking up in a strange city.
All Case 53s were marked with the same brand, tattoo, or mark; resembling variously a Greek Omega, a strange latin 'U', or even a stylized 'C'.
Case 53s were monstrous in appearance, though exceptions like Shamrock exist. As the years passed Case 53's were increasingly less "monstrous" as time went on. Faultline estimated that four out of five monstrous parahumans were Case 53s.
Case 53s were the results of experiments by Cauldron, successful in creating parahumans who did not immediately die from their physical mutations. They had their memories erased by the Slug to prevent them from sharing Cauldron's secrets, and Cauldron's symbol (a "C" drawn to resemble a stylized cauldron) branded or tattooed onto them with an ID number hidden in the right ‘arm' of the tattoo that each subject received; disguised as small spots where the tattoo hadn't taken.
Case 53s were usually taken from situations where they were about to die, their injuries healed or compensated for by their powers. Cauldron would experiment on these "subjects" by giving them doses of formula to test the results. Only two in five survived. Those who were physically transformed, becoming monsters, were known as "deviations" or "deviant cases" regardless of whether they were test subjects or customers. This possibility could be reduced using the balance formula, but it also reduced the strength of the resulting powers.
Only about two-thirds of Case 53s are monstrous. Some Case 53s were put towards the "Nemesis program", released with their memories erased and key weaknesses inserted into their psyches. Having noticed that Scion reacted aversively to some Cauldron capes, Cauldron deliberately spread Case 53s in areas where they were active, in order to distract him. Less than a hundred "deviants" were released onto Earth Bet. The vast majority were kept as prisoners in second basement level of the Cauldron Compound. Some of them became brainwashed Cauldron operatives.