Complex sentence: He worked intensively with the magical use of the Armanen Futharkh runes but as this was in conflict with the Nazis occultism he turns (ed) to other occult themes, such as the magic of the planets and the ancient books of magic (Grimoires).
Split into simpler sentences: He worked intensively with the magical use of the Armanen Futharkh runes. When this came in conflict with the Nazi regime he turned to other occult themes, such as the magic of the spheres and the ancient books of magic (Grimoires).