Who is Rachel Weintraub from The Rise of Endymion and what is their importance?

Rachel Weintraub is one of the original Hyperion pilgrims. She was later exposed to an anti-Time field from Hyperion's Time Tombs while studying the tombs as a graduate student. From the time of her exposure, Rachel began to age backward, becoming younger and younger until she became an infant and was given to the Shrike. Rachel returned from the future to guide Fedmahn Kassad, her lover, to his destiny.