Final answer:
Celia plays a ritual called the epopteia every night, which is part of the initiation into the highest degree of the Mysteries. This ritual plays a big role in the religious practices and beliefs associated with the Mysteries.
Step-by-step explanation:
Celia plays a ritual every night called the epopteia. It is a part of the initiation into the highest degree of the Mysteries. The exact order of the program is unknown, but it is suggested that it gradually builds up towards a climax. While we don't have specific details about what Celia's ritual entails, it is referenced that a phallus was shown to the epoptai as part of the initiation process. This ritual plays a big role in the religious practices and beliefs surrounding the Mysteries, and it is likely seen as an important and sacred ceremony.