Hello i just finished reading the book for the first time and it left me with a few questions

I know the conversation with mikhail on the way to Reich's station shined a different light on the "ghosts of the dead in the pipes" and implied that the darkness fear and low decibel frequencies where doing wonders to everyone at that point in the story but theres some details about him that never got answered

-the vision he had of the man dressed in white soon before he met artyom(presumably hunter)

-The note he left at artyom's homestation near the end of the book that read "those who are brave and patient enough to stare into the void their whole lives will be the first to see a flicker of light in it"

Theres no way to logically explain the dream of hunter. What had compelled Khan to travel all the way to artyom's homestation to deliver the note? was it foreshadowing of the connection with the dark ones? If it was would khan have somewhat of a connection to them to? What can explain the phenomina of the seeming mysticism around those two points? Just what is he?