Question: Who directed the film based on the same person's novel "Legion"?

Context paragraphs:
The Eagle (2011 film): The Eagle is a 2011 epic historical drama film set in Roman Britain directed by Kevin Macdonald, and starring Channing Tatum, Jamie Bell and Donald Sutherland.  Adapted by Jeremy Brock from Rosemary Sutcliff's historical adventure novel "The Eagle of the Ninth" (1954), the film tells the story of a young Roman officer searching to recover the lost Roman eagle standard of his father's legion in the northern part of Great Britain.  The story is based on the Ninth Spanish Legion's supposed disappearance in Britain.

Desert Sands: Desert Sands is a 1955 American adventure film directed by Lesley Selander and written by Danny Arnold, George W. George and George F. Slavin.  The film stars Ralph Meeker, Marla English, J. Carrol Naish, John Carradine, Ron Randell, John Smith and Keith Larsen.  The film was released on November 18, 1955, by United Artists.  The film was based on the 1954 novel "Punitive Action", one of a series of French Foreign Legion novels written by John Robb.  Unlike many Foreign Legion films the film was set in the 1950s.

Beau Geste (1966 film): Beau Geste is a 1966 film based on the novel by P. C. Wren filmed by Universal Pictures in Technicolor and Techniscope near Yuma, Arizona and directed by Douglas Heyes.  This is the least faithful of the various film adaptations of the original novel.  In this version, there are only two brothers, rather than three, and there are no sequences showing Beau's life prior to his joining the Legion.

Diary ng Panget: The Movie: Diary ng Panget (lit.  Diary of an Ugly Person) (also known as Diary ng Panget: The Movie) is a 2014 Filipino teen romantic comedy film based on the best-selling novel of the same name written and published on Wattpad by Denny R. The film was directed by Andoy Ranay and stars Nadine Lustre, James Reid, Yassi Pressman, and Andre Paras.  It was distributed by Viva Films and released on April 2, 2014, in theaters nationwide.

The Exorcist III: The Exorcist III is a 1990 American supernatural horror film written and directed by William Peter Blatty.  It is the third installment of "The Exorcist" franchise and a film adaptation of Blatty's novel, "Legion" (1983).  The film stars George C. Scott, Ed Flanders, Jason Miller, Scott Wilson and Brad Dourif.  This is the only "The Exorcist" film not to be distributed theatrically by Warner Bros., though Warner Bros. subsequently gained international distribution rights.

Legion (Blatty novel): Legion is a 1983 horror novel by William Peter Blatty, a sequel to "The Exorcist".  It was adapted into the movie "The Exorcist III" in 1990, and is part of The Exorcist franchise.  Like "The Exorcist", it involves demonic possession.  The book was the focus of a court case over its exclusion from "The New York Times" Best Seller list.

The Border Legion (1918 film): The Border Legion is a 1918 American silent Western film directed by T. Hayes Hunter and starring Blanche Bates, Hobart Bosworth, and Eugene Strong.  The film is based on the 1916 novel "The Border Legion" by Zane Grey.  The film marked the screen debut of Blanche Bates.  "The Border Legion" was released on August 28, 1918.  Following the acquisition of distribution rights by Goldwyn Pictures, the film was rereleased in the United States on January 19, 1919.  It is not known whether the film currently survives.

The Border Legion (1940 film): The Border Legion is a 1940 American Western film directed by Joseph Kane and written by Olive Cooper and Louis Stevens.  It is based on the 1916 novel "The Border Legion" by Zane Grey.  The film stars Roy Rogers, George "Gabby" Hayes, Carol Hughes, Joe Sawyer, Maude Eburne and Jay Novello.  The film was released on December 5, 1940, by Republic Pictures.

Beau Sabreur: Beau Sabreur is a 1928 American silent film directed by John Waters and starring Gary Cooper and Evelyn Brent.  Based on the novel "Beau Sabreur" by P. C. Wren, who also wrote "Beau Geste", the film is about a desert-bound member of the French Foreign Legion who exposes a betrayer to the Legion and is then sent on a mission among the Arabs to conclude the signing of a crucial peace treaty.  Produced by Paramount Famous Lasky Corporation and distributed by Paramount Pictures, only a trailer exists of this film today.  The released feature version is a lost film.

The Border Legion (1924 film): The Border Legion is a lost 1924 American Western silent film directed by William K. Howard and starring Antonio Moreno and Helene Chadwick.  Written by George C. Hull and based on the 1916 novel "The Border Legion" by Zane Grey, the film is about a cowboy who is wrongly accused of murder and is rescued by the leader of a band of Idaho outlaws known as the Border Legion.  When the outlaws kidnap a young woman, the cowboy knows that he must help the woman escape.  The film premiered on October 19, 1924 in New York City and was released in the United States on November 24, 1924 by Paramount Pictures.

Supporting paragraphs: Legion (Blatty novel) The Exorcist III
Answer: William Peter Blatty