Final answer:
The provided excerpts do not contain the characters Agatha or Sophie, nor the phrase 'Corpadora volvera.' Without more context or direct references to the related story, it is impossible to accurately answer why Agatha wanted Sophie to say this phrase.
Step-by-step explanation:
The passage provided does not give us enough contextual information to understand why Agatha may want Sophie to say Corpadora volvera. Typically in literature, a phrase like this could be part of a spell, incantation, or some pivotal plot device, however, without specific references to a story or book which this line comes from, it is impossible to provide a definitive answer. Addressing questions about plot elements, character motivations, or symbolic meanings often requires direct passages or summaries from the text. Instead of this phrase, various literary excerpts from other unrelated works are provided, none of which contain the characters Agatha or Sophie, nor the phrase Corpadora volvera.