Ghouls
Prolonged exposure to radiation will eventually either kill a human or, if they are more fortunate (or maybe less fortunate) mutate them into a ghoul. This depends on the genes of the victim. The mutating process takes months, or even years. They are repulsive but they are as smart as any human. They live longer than normal humans and they are also immune to radiation (in canon, yes, but due to game mechanics, they are not immune to radiation in 2238).
Ghouls settled in a few places around the wasteland. Necropolis, at first, was the home of the ghouls, but the town was destroyed by the Master's army. Most of the inhabitants managed to escape and moved to the towns of Broken Hills or Gecko, which are ghoul-friendly. Harold runs Gecko and the Poseidon Power Plant in town provides a sweet and warm radiation dose to nearby ghouls... They love it :) The town of Gecko suffers from problems with Vault City politics, combined with increasing discrimination which have contributed to the decline of the town.
Glowing ones
Some ghouls have suffered a very large dose of radiation exposure, and over time this causes them to glow in the dark. They are supposed to emit radiation, but they do not (yet ?) in FOnline: 2238. They are occasionally considered outsiders by normal ghouls, and are often banned by them, but such things do not happen in the biggest ghoul communities.
