Proposed Canon
First Appearance: LIAB Epilogue 19
Bill is the Dollamancer of Transylvito. He is said to be a pervert, and spends his spare time working on a hideous, perverted monstrosity of a doll as a hobby. He wears a pair of goggles, which may be a magic item, and an apron.
Given his decidedly creepy and perverted tastes, it is possible that he has a talent for Shockamancy.
 Real World References
Bill appears to be a reference to "Buffalo Bill," the killer in the movie "Silence of the Lambs," who keeps his victims in a pit in the basement of his house.