Premise: Vampires appear throughout Stephen King's fictional multiverse. They appear in the novels "'Salem's Lot", "", "", and ""; the short stories "One for the Road", "The Night Flier", "Popsy", and "The Little Sisters of Eluria"; and are mentioned in a number of other stories. Marvel Comics' "The Dark Tower: End-World Almanac" includes a detailed entry on their categorization.
Hypothesis: The Dark Tower: End-World Almanac featured vampires.