Final answer:
Auralia figures out that Diana gives the bulla its power through her Thessalian incantations and secret rites celebrated by her.
Step-by-step explanation:
In the given text, the character Auralia figures out that Diana gives the bulla its power through her Thessalian incantations and the secret rites celebrated by her. Auralia mentions how Diana, who is associated with the night and silence, uses her anger and power against the enemies' houses, and how Diana's power is compared to that of the barbarian Medea. It is evident that Diana's involvement and her rituals play a significant role in bestowing power upon the bulla.