Since the earliest versions of The Silmarillion legendarium as detailed in the History of Middle-earth series, Sauron underwent many changes. The prototype or precursor Sauron-figure was a giant monstrous cat, the Prince of Cats. Called Tevildo, Tifil and Tiberth among other names, this character played the role later taken by Sauron in the earliest version of the story of Beren and Tinúviel in The Book of Lost Tales in 1917.