Responses
What I remember from people who read the novel comment here is...
... That Magnus would found out who she really is, later, after he abandon and locked up Ilyana because he became bored of her.
He prevents her of her senses If I remember correctly. After her escape and her hiding in the Dark Night... She decides to go with Magnus and told him later who she really is.
To the ones who read the novel: does Mag found out Iliana is not the real Iliana but someone else? Or he still keep thinking she is the same crazy Iliana?