Ritual
There were some, what to our modern eyes would seem, very barbaric and strange cults and practices during ancient times and even after the start of the current era. The cult of Mithras, for example, had a baptism-like ceremony which involved the person - male, women were not allowed to join the cult - crouching in a pit while a bull was slaughtered on boards above his head. The Dionysians would eat the raw flesh of sacrificial animals, thinking they were eating the body of the god himself. Followers of Attis would castrate themselves as the god did in the legend.