An IDOLA is a creature that has been infected by the dark energies that emanate from the Del Crystal which is often referred as D-Cells. The process is both slow and extremely painful, often resulting in the infected individual beginning to lose grip of their individuality before their body parts begin to mutate into different shapes depending on their general physical appearance and body mass.
Common mutations often involve bladed protrusions from certain parts of the body (most often the hands or feet) and/or the epidermis growing a thick exoskeleton. Sometimes the mutation will imbue the infected with arcane energy allowing them to cast powerful dark magic.
Sometimes the D-Cells will infect synthetic material as well and rewrite it's programming to fit a certain role.