"Touched by the Crimson King" is a reference to the Crimson King, the main antagonist of the series.
However, the song itself seems to be about Randall Flagg, one of the King's many servants.
"The Gunslinger" is referring to Roland of Gilead, the protagonist of the piece.
Throughout this piece there are references to the fifth book of the series,
'Wolves of the Calla' (e.g., 'come-commala', 'say thankya')
"Terror Train" is a reference to Blaine, the insane train in the Dark Tower.
"Beneath These Waves" was directly inspired by Moby Dick and one's man struggle with nature
and which ties in with repeated references in the Dark Tower novels drawing parallels between Roland of Gilead
and Captain Ahab.
"Wicked Witch" is Kürsch's interesting interpretation of the Wizard of Oz,
which is also referenced in the fourth installment of the "The Dark Tower" series of novels Wizard and Glass
"Dorian" was inspired by Oscar Wilde's novel The Picture of Dorian Gray,
which again bears some relation to the character of Roland of Gilead.