Severin Films becomes possessed by obscure Italian horror with BYLETH: THE DEMON OF INCEST on Blu-ray.

Ever since he was a child, Lionello, the Duke of Shadwell (Mark Damon, NAKED YOU DIE) has had a delicate temperament and has suffered multiple nervous breakdowns, the latest of which coincides with the bizarre murder of prostitute Dolores. He also has strange hang ups about sex, the nature of which we learn when his sister Barbara (Claudia Gravy, ¡MÁTALO!) returns from Venice married to older Giordano (Aldo Bufi Landi, SUPER STOOGES VS THE WONDER WOMEN). Giordano intuits pretty quickly that Lionello does not like him, although only Barbara truly knows why. After seeing them in bed together, Lionello searches among the belongings of his father – who fled England to avoid a witchcraft trial and later died in a mysterious fire – and comes across a parchment from an occult tome. When Barbara's maid Gisella (Caterina Chiani, SEX OF THE WITCH) propositions Lionello after he sees her with the stable groom, she is also murdered in the same manner as the prostitute, and the suspicion of the local judge (Alessandro Perrella, THE GIRL IN ROOM 2A) turns to Lionello despite the deflections of Barbara and the local doctor (Fernando Cerulli, WATCH ME WHEN I KILL). When the local priest (Antonio Anelli, WHAT HAVE YOU DONE TO SOLANGE?) voices his suspicions that the signature stab wounds on the villains are the mark of the demon Byleth, however, Barbara and Giordano start to fear for the safety of his cousin Floriana (Silvana Pompili) who Giordano invited in order to foster Lionello's interest in her.

After starring in "The Wurdalak" segment of Mario Bava's BLACK SABBATH – an Itailan co-production with American International for whom Damon had previously co-starred in Roger Corman's THE FALL OF THE HOUSE OF USHER – Damon stayed on in Italy, appearing in a handful of spy films and spaghetti westerns like REQUIESCANT and JOHNNY YUMA before getting into production to drum up roles for himself. It appears that BYLETH was highly influential as the film bears some similarities to the Damon starring/producing vehicle Luigi Batzella's THE DEVIL'S WEDDING NIGHT the following year right down to the scoring of Vasili Kojucharov (SS EXPERIMENT LOVE CAMP); although, like jobbing director Leopoldo Savona – who next helmed the more interesting giallo DEATH FALLS LIGHTLY – Kojucharov's strings never spill over into the bombast of the Batzella film. However more dramatically ambitious the story and Damon's performance, the film has the overall feel not of a golden age Italian gothic and more in common with the likes of NUDE FOR SATAN or BLOODSUCKER LEADS THE DANCE in its clash of stodgy gothic and softcore nudity. Indeed, it appears as though someone recognized this as some obvious inserts have been added into the sex scenes. They are not hardcore but slightly more graphic – including a frontal nude shot of male hands removing some very anachronistic panties from a female form – but their head-on angles in the sex scenes as well as the flatter lighting of the additions during Lionello's delirium montage late in the film. IMDb lists uncredited Karin Lorson (Joseph Sarno's BIBI) and Florian Endlicher (VARSITY PLAYTHINGS) as Dolores and her lover in the prologue. Since the characters are mentioned in the dialogue in Italian version, I would assume that the two actors are not the actors who play the characters but the body doubles for the extra shots since all of their other credits are sex comedies, and that it was the German distributor who added the footage (although we have only the German negative here which seems to vary from the Italian since the import DVD edition has a featurette comparing the transfer to the Italian VHS).