In Bram Stoker’s "Dracula" the eponymous Count was weakened by sunlight, but it did not kill him. Trying to trace where the idea of vampires exploding in to a cloud of dust or catching on fire when in sunlight seems to lead to the 1922 movie Nosferatu. In the movie, Count Orlok needs to sleep by day as the sunlight would otherwise kill him.

One theory goes that this element was introduced in order to differentiate the story somewhat from "Dracula" which it quite proudly stole most of it's plot from.

The attempts at differentiating were not enough however and the movie company Prana Film was forced to declare bankruptcy after Florence Stoker, Bram’s widow and holder of the estate, sued the company for copyright infringement and won.

Campaign: “Curse of Strahd”, Dungeons & Dragons

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