Complex sentence: The White Witch says that she needs a drop of "Adam's blood" to live again, which she tries to coax from Caspian and then from Peter with promises of lending her great powers to their cause against King Miraz once she is made whole.
Split into simpler sentences: The White Witch says that she needs a drop of "Adam's blood" to live again. She tries to coax this first from Caspian and then from Peter, promising to lend her powers to their fight against King Miraz once she is made whole.