Based in part upon a legend that Max Schreck was in reality a vampire which is why he played the role of Orlock/Dracula so well. Some variations of the legend suggest that Nosferatu (1922) was the only film Schreck made, though in reality he was already a stage and screen veteran by the time Nosferatu was shot, and would appear in many non-Vampiric roles before his death in 1936.
Max Schreck (Willem Dafoe) recites Tennyson's poem 'Tithonus' at one point: 'The woods decay, the woods decay and fall, the vapors weep their burthen to the ground...' This is apropos, because the poem is about a character from Greek mythology who was immortal even though he continued to age. Just like Schreck, this made him a tragic figure.
The trivia item below may give away important plot points.
Originally titled "Burned to Light" in a reference to the filmmaking process (and the vampire's ultimate fate in the film); the title change came about because apparently some people misread the title as "Burn Ed to Light."