Belphegor is one of the Seven, corresponding to Acedia — Sloth. His method is not torpor but seduction: he approaches through brilliant, irresistible ideas — inventions that will make you rich, discoveries that will change everything — and then watches as the idea proves unfinishable, the inventor grows apathetic, and the work collapses under the weight of its own potential. He does not oppose effort. He makes effort seem unnecessary, because the idea is already perfect in the imagination and the execution can only diminish it.
In Helen Marsden's analysis of the Seven's coordinated function, Belphegor is Acedia ensuring no one cares enough to stop them. This is the tail of the operation — not the corruption, not the seduction, not the violence, but the long institutional indifference that settles after the other six have done their work and makes certain that no inquiry follows, no record survives, no one picks up the thread. The genius of Acedia as a weapon is that it looks like peace.