From The Vault

Glowing Ones are ghouls who absorbed so much radiation that they glow in the dark. They are often considered outsiders even by other ghouls. The Glowing Ones also emit radiation, so they can be dangerous to normal humans.

In Necropolis, the Glowing Ones lived in the remains of Vault 12, and there was an animosity between them and the "normal" ghouls led by Set, who inhabited the ruins of the town. After Necropolis was overrun by the super mutants, the Glowing Ones who left the town lived much more harmoniously with the other ghouls (not to mention normal humans and super mutants).

[edit] SPECIAL

In terms of the SPECIAL mechanics, Glowing One is a ghoul-only trait from Fallout Tactics.

If you are a Glowing One, your glow eliminates modifiers from light in combat for both you and your enemies. In addition, you gain a +50% bonus to Radiation Resistance, but everyone around you gets radiated a bit.

[edit] Appearances in games

Glowing Ones have appeared in all Fallout games. The Glowing One trait is available only in Fallout Tactics, as it is the only game which allows you to create ghoul characters.