August Underground's Mordum (2003)

Obsessed with inflicting pain on others while recording everything on tape, brutal serial killer Peter Mountain is still at large. And after the shocking events in August Underground (2001), Peter now makes friends with two new perverts: sadomasochistic Crusty and her mentally challenged brother Maggot. This time, the diabolical sadists are hell-bent on broadening their horizons, willing to experiment with self-mutilation, decaying corpses, evisceration, and rape. However, when yet another psychopath enters the picture, eager to hang out with them, depravity reaches new heights.