If a person cast no shadow at all, he couldn't be alive. His existence became meaningless.Execrating Apophis by destroying his shadow would cut his connection to the mortal world completely. He'd never be able to rise again. I finally understood why he'd been so anxious to burn Setne's scrolls, and he was afraid of this spell. (Carter Kane)
The Serpent's Shadow (The Kane Chronicles Book 3) (ed. Penguin UK, 2012) - ISBN: 9780141967547