These are not Goblins of mythology, but victims of fallout. Many children that were dosed with strong radiation resulting from the bombing were killed, however some survived. The result of the radiation stunted their physical and mental growth and distorted their bodies. They were dubbed "goblins" because of their likeness of appearance and demeanor to those described in fantasy. Some have instead taken to calling them "pygmies" as well.
Goblins can be found all over Calydon, but reside in greater numbers near sources of radiation, such as the GRIEF.
While they have no real culture to speak of, small groups of Goblins cooperate with other Radchildren to