Nunsploitation. Jesus...
Most of these are less horror than kinky soft core pictures with the odd sacreligious overtone and Catholic baiting shenanigans: The Other Hell and Flavia the Heritic are probably the best known genre entries -- the formewr something similar to Charles Band's Catacombs or a bad Stuart Gordon rip off, the latter a more exploitation friendly cash in on The Devils. Ken Russell repaid the favour for a segment of Crimes Of Passion when Kathleen Turner dons a habit and fishnets.
The genre gained small credibility (??) when La Dolce Vita star Anita Ekberg toplined the sleazy Killer Nun -- best described as a hypothetical telling of might have happend if Maria from The Sound Of Music had discovered bars and drugs instead of the Von Trapps. And Walerian Borowczyk was the bigest proponent of the art porn angle, churning out the odd sexy nun picture (Beyond The Convent Walls and a segment of Immoral Tales). And this is probably the most prominent, yet least interesting, facet of the genre -- innocent young nuns corrupted by older lebian nuns of creaky monks. Pretty dull. And this is exactly the kind of thing Nigel Wingrove of Redemption/Salvation decided to cash in on throughout the 90s. He's still churning them out, I believe.
A more solid genre piece though is Dark Water. Directed by brit Mario Baino, before he disappeared back into obscurity, it's a funky little low budget picture about a young woman relocated to a remote islnad convent where demonic goings on are naturally afoot. Lensed in the scorched earth terrain of Georgia (Russia) and featuring a wonderfully fetid Fulci-esque atmosphere, it also has a typically obfuscatory Lucio-like "plot". Pretty good. And of course, due to that fact, it's unavailable on DVD.