Based on a book I've never read (Aleksei Tolstoy's The Family of the Vourdalak), Night of the Devils deals with the supernatural creature known as the wurdulac (also spelled wurdalak, vourdalak or verdilak), a type of Eastern European vampire that is compelled to drink the blood of its loved ones, thereby converting the whole family.
Lumber importer Nicolas (Gianni Garko) encounters such monsters in a Yugoslavian forest. After pranging his car, he sets off on foot to find help, eventually meeting a family who live in a house in the woods, where he is invited to stay the night. Nicolas is intrigued when his hosts barricade all of the doors and windows at nightfall; he eventually discovers that the family is plagued by a wurdulac that comes a-calling once it is dark.
With a very measured pace, this isn't going to be for everyone, but fans of atmospheric Euro-horror will be delighted by the creepy vibe throughout and some genuinely tense moments, the best being Nicola's frantic escape from the woods in his car (attacked by wurdulacs and mocked by ghoulish wurdulac children), and the gripping finalé, which packs a neat downbeat twist.
Meanwhile, those who enjoy a spot of gore and nudity will be pleased to know that are some juicy moments of splatter (a woman's face exploding, a beating heart removed from a body, severed fingers, and several bloody stakings, all courtesy of FX man Carlo Rambaldi) and a fair amount of T&A (ravishing Agostina Belli, as Nicola's love interest Sdenka, sheds all for her art, while Teresa Gimpera has her top torn open by one of the vampiric kids).
N.B. The wurdulac also appears in Mario Bava's classic horror compendium Black Sabbath, a film I've yet to see (I know, I know... and I call myself a horror fan).