Elixir is the debut young adult novel co-written by American entertainer Hilary Duff with Elise Allen.

Clea looks over some old photos of herself and notices that a mysterious man wearing black appears in the background of all of them, including several where he is floating in the air.

She brings up the phenomenon to her friend Ben, who informs her that her father had noticed the man years earlier and investigated for a while before deciding that he was a harmless guardian spirit.

Magda then tells Sage that the only way she knows of to end the curse and save Clea is for him to commit suicide using a magical knife that negates his immortality.

Sage decides to end his life on a beach but Clea, unknown to him, calls The Saviors and informs them of their location.

Duff said, in an interview she gave to Seventeen Magazine about the creation of Elixir, "I have been playing with the idea for a few years now.

Duff informed the magazine that she had had the idea in her mind for a long time, first with a series of short scripts, but then, following encouragement from her mother, she decided to convert the concept into a book, recruiting Elise Allen to assist her with the writing.

[1] The New York Post wrote, "It has everything: romance and the supernatural; a globe-trotting Hillary Clinton-esque mom; characters with names like Sage and Clea...and a shout-out to Page Six!

MTV also said that "Elixir is crying out for a movie adaptation" and suggested that maybe Hilary Duff herself should take the main role.

[3] Elixir also reached the New York Times' Best Sellers List at #10 in Children's Chapter Books for one week.

[4] Duff had already stated multiple times that she would write a couple of sequels to Elixir, all in collaboration with Allen.