One thing to note that there seems to be a dualism going on between Kris and the Knight where Kris has trouble in the dark world (mustn't enter a dark world without a soul according to the phone) and the Knight has trouble in the light world (according to Susie).
Plus, look at these lyrics:
>Come follow me into the dark
>With your heart as the ark
>Which shall shine you the way
>Because I'm with you in the dark
>With your heart as my mark
>Which shall guide you the way,
>through the waves