Although perhaps a little too excitable when around firearms, Phantom enthusiastically welcomes you to the ragtag Pitt Raider family (if you aren't massacring them all). He can share his RadAway with you once per day.
Phantom is in charge of treating radiation poisoning among the raiders.
Once a day, the player can ask Phantom for radiation treatment, resulting in Phantom giving the player a dose of RadAway.
He will get defensive if you ask him "You think you work harder than the slaves?". He will reply "Fuck yes we do", and will back himself up by mentioning how raiders have to go through so much just to get supplies and food for the slaves.
Phantom is most likely a reference to Pittsburgh's best known and most popular pop-culture emporium, Phantom of the Attic, which is a comic book and RPG gaming store located in the Oakland (Uptown) section of the city.
Phantom might also be a reference to Pittsburgh's only amusement park, Kennywood, that has a roller coaster called "The Steel Phantom", which was later rebuilt and renamed the "Phantom's Revenge".