Complex sentence: To Guido von List, Friedrich Bernhard Marby and Siegfried Adolf Kummer the runes represent the key to esoteric understanding; to Spiesberger they were just onemore tool to be used by any individual magician.
Split into simpler sentences: To Guido von List, Friedrich Bernhard Marby and Siegfried Adolf Kummer the runes represent the key to esoteric understanding. To Spiesberger, they were just one more tool to be used by any individual magician.