Oswald is a non-feral glowing one living in Nuka-World's Kiddie Kingdom in 2287. He has the same abilities as feral glowing ones in that he uses bursts of radiation to heal and revive nearby feral ghouls. As a former magician employed by Nuka-World, Oswald believes his ability to resurrect dead ghouls to be genuine magic.
Oswald is one of the original survivors from a band of employees that took shelter in Kiddie Kingdom during the bombing and immediate fallout from the Great War. After time had passed, the entire group began changing into ghouls due to radiation leaking in. One by one, the survivors began turning feral, leaving Oswald and Rachel as the last non-feral ghouls in Kiddie Kingdom. He takes on a role as a protector of his former friends, strongly believing that being a feral ghoul is a sickness (that he and the other survivors via terminal entries call "the Affliction") that can be cured. He is in wait of one of the other original survivors, Rachel, whom he believes will return with the cure some day.
He hates the raider clans that have settled in Nuka-Town, and scares them away from Kiddie Kingdom through a combination of supposedly paranormal powers and mist-sprayers that swamp Kiddie Kingdom with lethal radiation.
If Oswald is left alive at the end of his quest and goes in search of a cure, RedEye will comment on Nuka World radio that the "Overboss found the one ghoul left with half a brain and gave him a job". You may hear this comment even if Oswald is killed to complete the quest.
Like any glowing one, Oswald can use radiation to heal fellow ghouls.
He also uses smoke bombs and tricks he got from his career as a magician to seemingly appear and disappear at will.
Oswald is also unique in that he remains sane while the rest of his community became feral. It is not explained in-game why this is.
Oswald gives off a small amount of radiation unlike other sentient glowing ones such as Jason Bright.
Oswald is the sixth sentient glowing one to appear in the entire Fallout franchise.
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
Oswald's full name is "Oswald Oppenheimer" which is most likely a reference to the real-life theoretical physicist named J. Robert Oppenheimer, who was one of the scientists on the Manhattan Project.
End of information based on unverified behind the scenes information.
If the player is wearing power armor, Oswald will comment: "What's wrong, Tin Man? Having trouble finding the Wizard? Personally, I would have figured you for the Scarecrow." This is a reference to The Wizard of Oz.