Vlad Dracula - The Impaler?

Few historical figures have captured the imagination of later generations as much as the Wallachian prince Vlad III Drăculea (* c. 1431). He is the historical model for the vampire lord Dracula - the world-famous protagonist of countless films and books, not least Bram Stoker's (1847-1912) novel "Dracula," published in 1897. But how did the ruler and army commander, who was quite recognized in his time, become the 'Prince of Darkness'? Which legends are true - which are not? And when and why did they come into being?