Fens Phantom

The Fens Phantom was a Boston-based serial killer heard in the dear detective tapes, operating out of the Fens Street sewer

Background
The Fens Phantom was a prolific serial killer in Boston before the Great War, who was presumed to have claimed dozens of Bostonian lives, displaying their corpses in the city sewers, which he had claimed as a "base of operations" of sorts.

Motives
The Phantom shows heavy frustration with society and societal norms, and how he views people as fake and transparent, using holotapes as a means to spread his vision to those that would listen. He voices this in his second detective holotape:

Appearances
The Fens Phantom appears only in Fallout 4.