There are three classifications of modifications applied to Experiments in the Pit, and they are Psychic, Genetic/Biological and Mechanical.
Psychics may have nothing about their appearance changed, but are wired to have special abilities which range from empathy to pyrokinesis, even the stimulating of fast cell growth for healing.
Genetic/Biological alterations range from minor shapeshifting to animal gene splicing to slowly evolving mutations, added limbs, heightened senses, and they can be as simple as increased muscle or bone strength or higher output of pheromones.
Mechanical changes are usually just that... cyborg prosthetics are the most common.
All psychic and most genetic powers require energy to use, which means acquiring and consuming food and finding safe places to rest become very important as overusing the modifications one has been given could lead to an early grave. Likewise, mechanical parts can fall into disrepair or become damaged if not properly cared for.