Question: What was the sequel to Bride of Frankenstein (a sequel itself) and the last in the series to star Boris Karloff as the monster?

Context articles: Boris Karloff
Mae Clarke
Charles D. Hall
Bride of Frankenstein
Son of Frankenstein
House of Frankenstein (1944 film)
Karloff (play)
The Evil of Frankenstein
Boris Karloff filmography
Starring Boris Karloff

William Henry Pratt (23 November 1887 – 2 February 1969), better known by his stage name Boris Karloff, was an English actor who was primarily known for his typecast roles in horror films that depicted the characters Frankenstein and the Mummy.
 He portrayed Frankenstein's monster in "Frankenstein" (1931), "Bride of Frankenstein" (1935), and "Son of Frankenstein" (1939), which resulted in his immense popularity.
 He also appeared as Imhotep in "The Mummy" (1932).
Mae Clarke (born Violet Mary Klotz; August 16, 1910 – April 29, 1992) was an American actress.
 She is best remembered for playing Henry Frankenstein's bride Elizabeth Lavenza, who is chased by Boris Karloff, in "Frankenstein", and also, for having a grapefruit smashed into her face, by James Cagney in "The Public Enemy".
 Both films were released in 1931.
Charles D. Hall ( April 20, 1888 – April 8, 1970) was a British-American art director and production designer.
 He is perhaps best remembered for his tenure at Universal Pictures, where he began his career during the silent era.
 He was art director for many of Universal's most famous productions of the 1920s and '30's: "The Phantom of the Opera" (1925), "All Quiet on the Western Front" (1930), the original Bela Lugosi "Dracula" (1931), the original "Magnificent Obsession" (1935), and the 1936 "My Man Godfrey" among them, as well as eleven films directed by James Whale, including the original Boris Karloff "Frankenstein" (1931), "The Invisible Man" (1933), "Bride of Frankenstein" (1935), and the 1936 film version of "Show Boat".
 Hall also worked on the 1929 part-talkie film version of "Show Boat", directed by Harry A. Pollard.
Bride of Frankenstein (advertised as The Bride of Frankenstein) is a 1935 American science-fiction horror film, the first sequel to Universal Pictures' 1931 hit "Frankenstein".
 It is considered one of the few sequels to a great film that is even better than the original film on which it is based.
 As with the first film, "Bride of Frankenstein" was directed by James Whale and stars Boris Karloff as The Monster.
 The sequel features Elsa Lanchester in the dual role of Mary Shelley and the Monster's mate at the end of the film.
 Colin Clive reprises his role as Henry Frankenstein, and Ernest Thesiger plays the role of Doctor Septimus Pretorius.
Son of Frankenstein is a 1939 horror film directed by Rowland V. Lee, and is the third entry in Universal Studios' "Frankenstein" series and the last to feature Boris Karloff as the Monster.
 It is also the first to feature Bela Lugosi as Ygor.
 The film is the sequel to James Whale's "Bride of Frankenstein", and stars Karloff,
House of Frankenstein is a 1944 American monster crossover horror film starring Boris Karloff and Lon Chaney Jr., directed by Erle C. Kenton, written by Curt Siodmak, and produced by Universal Studios as a sequel to "Frankenstein Meets the Wolf Man" the previous year.
 The cast includes a mad scientist (Karloff), the Wolf Man (Chaney), Count Dracula (John Carradine), a hunchback (J. Carrol Naish), and Frankenstein's monster (Glenn Strange).
 This "monster rally" approach would continue in the following film, "House of Dracula", as well as the 1948 comedy "Abbott and Costello Meet Frankenstein".
Karloff is a biographical one-man play about the life of film star Boris Karloff, written by Randy Bowser.
The Evil of Frankenstein is a 1964 British Hammer Film Productions film directed by Freddie Francis.
 It stars Peter Cushing and New Zealand wrestler Kiwi Kingston.
 The film's version of the Monster is noted for resembling the one in Universal Pictures' original "Frankenstein" series of the 1930s and 1940s, including the distinctive laboratory sets as well as the flat-headed look of Jack Pierce's monster make-up which had been designed for Boris Karloff.
 Earlier Frankenstein films by Hammer had studiously avoided such similarities for copyright reasons.
 However, a new film distribution deal had been made between Hammer and Universal.
 As a result, Hammer had free rein to duplicate make-up and set elements.
This is the filmography of Boris Karloff.
 Born as William Henry Pratt, he joined a touring company and adopted the stage name Boris Karloff.
 During these early stages of his career he was mostly left in obscurity.
 By 1919, Karloff found regular work as an extra at Universal Studios.
 Karloff's first significant hit film was in Howard Hawks's "The Criminal Code" (1931).
 While shooting "Graft", director James Whale convinced Karloff to star as a character in one of his most popular roles as Frankenstein's monster in "Frankenstein" which led to him becoming an overnight superstar.
 After "Frankenstein" and starring in several high-profile films such as "Bride of Frankenstein" and "Scarface", Karloff spent the remainder of the 1930s continuing to work at an incredible pace, but progressively more into less financially successful films.
 Karloff starred in a few acclaimed Val Lewton produced horror films of the 1940s and by the mid-1950s, he was a familiar presence on television hosting his own series including "Thriller" and "The Veil" and guest starring on such variety programs as "The Donald O'Connor Show".
Starring Boris Karloff is an American radio and television anthology series broadcast for 13 weeks, September–December 1949, on the ABC Television network.
 Boris Karloff was the host and occasional star, with music by organist George Henninger.
 Produced and directed by Charles Warburton, the series adapted short stories of mystery and suspense.