How does the author use foreshadowing in The Dark Tower VII: The Dark Tower?

In Chapter Four, we learn that Susannah has acquired an alternate personality, Mia,
who is impregnated by the Crimson King. Mia becomes her own being and gives birth to the child. Mordred clearly is influenced by the Crimson King's nature with his ability to turn into a spider, killing his mother. Susannah wounds the creature but is not able to kill him, foreshadowing that the Mordred will cause problems for them in the future.