Robert Jacobs, in his biography of the composer, observes that the "Nibelung Myth" on which Wagner based his entire "Ring" story was "very much a personal creation", the result of Wagner's "brilliant manipulation" of his sources. In the "Rheingold" text, Wagner used his imaginative powers to adapt, change and distort the stories and characters from the sagas. J.K. Holman, in his "Listener's Guide and Concordance" (2001), cites the Alberich character as typifying Wagner's ability to "consolidate selected aspects from diverse stories to create ... vivid, consistent and psychologically compelling portrait". While some characters' importance is enhanced in Wagner's version, others, such as Donner, Froh, and Freia, who are major figures in the sagas, are reduced by Wagner to roles of largely passive impotence.