He set up a lab near Wittgenstein (which was eventually converted into a pub named after him, Dippelshof), and at this point in his life historical records are vague on his activities and thus grew folkloric in nature. During this time, at least one local minister apparently accused Dippel of grave-robbing, experimenting on cadavers, and keeping company with the Devil. For the most part, Dippel kept to himself and his work; he perhaps even actively perpetuated the rumours that he had sold his soul to the Devil in exchange for secret knowledge, as relying on his reputation as a dark sorcerer better enabled him to find audiences with those willing to pay for his knowledge of the philosopher's stone and the elixir of life. He died at Castle Wittgenstein near Bad Laasphe, probably from a stroke, though some contemporaries suspected poisoning. A year before his death, he wrote a pamphlet in which he claimed to have discovered an elixir that would keep him alive until the age of 135. Connection to the novel Frankenstein Dippel's connection to the Castle Frankenstein gave rise to the theory that he was a model for Mary Shelley's 1818 novel Frankenstein; or, The Modern Prometheus, although that idea remains controversial. This hypothesis was probably first suggested by Radu Florescu in his book In Search of Frankenstein (1975), which speculated that Shelley (then Mary Wollstonecraft) visited the castle during her travels on the Rhine with Percy Shelley, where they might have heard local stories about Dippel, which by then would have grown legendary and notorious. Florescu also notes that the Shelleys reference a brief interaction while touring the countryside around Castle Frankenstein with students of the University of Strasbourg, of which Dippel was once a student; these students could have told them stories about the infamous alumnus. In addition, the Shelleys knew several members of the so-called "Kreis der Empfindsamen", a literary circle that met in Darmstadt from 1769 to 1773; Castle Frankenstein was frequently used as a location for their public readings, thus making it possible that Dippel's legends could have come up during conversations between those in the circle and the Shelleys. A local historian, Walter Scheele, believes that the legends told in the villages surrounding the castle were transmitted by Jacob Grimm to Mary Jane Clairmont, translator of Grimm's fairy tales and stepmother of Mary Wollstonecraft Godwin. Scheele also claims that, in 1814,