Final answer:
The excerpts do not provide information about Dr. D'Avrigny or Valentine, hence an accurate answer cannot be given to the question regarding what saved Valentine from death.
Step-by-step explanation:
What Dr. D'Avrigny discovered that had saved Valentine from death is not explicitly revealed in the texts provided.
The excerpts presented comprise different narratives and contexts which do not include a character named Dr. D'Avrigny or Valentine, and therefore, the question seems to be referring to a specific plot point that is not covered in the supplied information.
To accurately answer the question about Dr. D'Avrigny and Valentine, one would need context from the actual literary source where these characters appear.
It appears the descriptions are from various works of literature, potentially addressing themes like love, life, healing, and the power of nature, but without the correct context, providing an answer to the question would be mere speculation.