Butchered by the producer...

The following excerpt (which includes an informative telegram from the director to the star) is from "The Complete Films of Vincent Price" by Lucy Chase Williams:

The project had a long history. AIP announced they had acquired the rights to the book "Devilday" in April 1970; at that time Price was to star, and "Dr. Phibes" director Robert Fuest was to direct. By the end of November 1971, Nicholson and Arkoff were listed as co-producers of a screenplay by Murray Smith, and shooting was scheduled for mid-1972. The project surfaced again in April 1973 when Arkoff (following partner Nicholson's untimely death) concluded an agreement with Max Rosenberg and Milton Subotsky of Amicus Pictures to produce "The Revenge of Dr. Death," with a screenplay by former film publicist Greg Morrison.

Production was slated to begin in May with one-time editor Jim Clark directing. The picture, which was retitled along the way, way filmed at Twickenham studios and on various London locations. Many of the scenes were shot at Pryford Manor, a fifteenth-century residence often used by Queen Elizabeth I. Clips presented as early "Paul Toombes" pictures came from "Pit and the Pendulum," "Tales of Terror," "The Masque of Red Death," "House of Usher" and "The Raven."

After Vincent had wrapped his scenes for "Madhouse" and returned to Los Angeles, he received a lengthy, anguished lament from Jim Clark, who was "in a miasma of impotent rage." The director was having terrible disagreements with Subotsky, "who has bulldozed his way into the cutting room and is at this very moment cutting a swath through the film... I feel responsible toward you, and as a friend I shall defend our mutual interest just as long as I can -- but I fear, in the end, that we shall both suffer at their hands, and it is your name that will sell the film, and mine that will receive the blame for making a poor picture... They are retaining all the action, of course -- but every time anyone opens their mouth Milton tries to cut out the line -- for no other reason than 'it bores me' or 'we don't need it.' It is pure butchery and I don't really know why I'm surprised."