Question: Who is the game designer born in 1950 who is best known for his work on materials for the "Dungeons & Drangon fantasy role-playing game?
Context: Dungeons & Dragons Immortals Rules, written by Frank Mentzer, is a boxed set for the "Dungeons & Dragons" ("D&D") fantasy role-playing game first published by TSR in 1986 as an expansion to the "Basic Set". Brian R. James (born 1974) is an award winning game designer and patent holding software engineer.  As a writer, Brian is best known for his online and print works for the "Dungeons & Dragons" fantasy role-playing game published by Wizards of the Coast.  In game design circles, Brian is highly regarded for his deep knowledge of the Forgotten Realms campaign setting and its extensive history.  In 2012 Brian won a Silver ENnie Award for "" and he has been nominated for other ENnie Awards and Origins Awards. Forgotten Realms is a campaign setting for the "Dungeons & Dragons" ("D&D") fantasy role-playing game.  Commonly referred to by players and game designers alike as "The Realms", it was created by game designer Ed Greenwood around 1967 as a setting for his childhood stories.  Several years later, Greenwood brought the setting to the "D&D" game as a series of magazine articles, and the first Realms game products were released in 1987.  Role-playing game products have been produced for the setting ever since, as have various licensed products including sword and sorcery novels, role-playing video game adaptations (including the first massively multiplayer online role-playing game to use graphics), and comic books.  The Forgotten Realms is one of the most popular "D&D" settings, largely due to the success of novels by authors such as R. A. Salvatore and numerous role-playing video games, including "Pool of Radiance" (1988), "Eye of the Beholder" (1991), "Baldur's Gate" (1998), "Icewind Dale" (2000) and "Neverwinter Nights" (2002). Neverwinter Nights 2 is a role-playing video game developed by Obsidian Entertainment and published by Atari, Inc. It is the sequel to BioWare's "Neverwinter Nights", based on the "Dungeons & Dragons" pencil and paper fantasy role-playing game.  "Neverwinter Nights 2" utilizes an adaptation of the "Dungeons & Dragons" 3.5 edition rules.  Players create player characters to represent themselves in the game, using the same character creation rules as found in the "Dungeons & Dragons" game.  They may gain the assistance of additional party members, and they eventually acquire a keep that can be used as a base of operations.  "Neverwinter Nights 2" is set in the Forgotten Realms campaign setting—in and around the city of Neverwinter.  The story is mostly unrelated to "Neverwinter Nights" and follows the journey of an orphaned adventurer investigating a group of mysterious artifacts known as "silver shards" and their connection to an ancient, evil spirit known as the King of Shadows. Steve Miller is a game designer and editor who has worked on a number of products for the "Dungeons & Dragons" fantasy role-playing game from Wizards of the Coast, and other role-playing games. Dwellers of the Forbidden City is an adventure module, or pre-packaged adventure booklet, ready for use by Dungeon Masters in the "Dungeons & Dragons" ("D&D") fantasy role-playing game.  The adventure was first used as a module for tournament play at the 1980 Origins Game Fair, and was later published by TSR in 1981 for use with the first edition "Advanced Dungeons & Dragons" rules.  The module was written by game designer David "Zeb" Cook, who partly ascribes his hiring by TSR to his work on this module.  In the adventure, the characters are hired to find an object taken to a lost oriental-style city, which has been taken over by a cult of snake-worshipers, the yuan-ti, and their servants, the mongrelmen and tasloi.  The module was ranked as the 13th greatest "Dungeons & Dragons" adventure of all time by "Dungeon" magazine for the 30th anniversary of the "Dungeons & Dragons" game in 2004. Tom Moldvay (Thomas Steven Moldvay, Nov. 5, 1948 – March 9, 2007) was a game designer and author most notable for his work on early materials for the fantasy role-playing game "Dungeons & Dragons" (D&D). Matt James (born 1981) is an American game designer and a decorated veteran of the United States Army.  As a game designer, James is best known for his online and print works for the "Dungeons & Dragons" fantasy role-playing game published by Wizards of the Coast, "Pathfinder" role-playing game by Paizo, and Privateer Press.  He has also designed game content for Wolfgang Baur's Kobold Press (formerly Open Design LLC).  In 2012 James won an ENnie Award for "" and has been nominated for several Origins Awards.  In 2014, James won an ENnie Award for "". The Dungeons & Dragons Adventure Game is the name of two companion accessories to the second and third editions of the "Dungeons & Dragons" fantasy role-playing game.  Designed as simpler, stand-alone versions of "Dungeons & Dragons", they feature a simplified ruleset, but with character progression that parallels the standard game.  However, for 3rd-level characters and higher, the standard "Player's Handbook" is still required.  The first version was published in 1999 for the second edition of "Advanced Dungeons & Dragons", while the second version was published in 2000 for the third edition of "Dungeons & Dragons". Jacob Franklin "Frank" Mentzer III (born in 1950), is an American fantasy author and game designer best known for his work on early materials for the "Dungeons & Dragons" (D&D) fantasy role-playing game.  He was a performing folk musician from 1968 to 1975, and played one concert at the White House during the administration of Richard Nixon.  He was an employee of TSR, Inc. from 1980–1986, spending part of that time as Creative Advisor to the Chairman of the Board, Gary Gygax.  He also founded the Role-Playing Games Association (RPGA) during his time with TSR.  He has been closely involved with the world's largest game auction at the Gen Con game convention since 1983, and is an expert on, and a major collector of, family boardgames and role-playing games.  After Gygax was ousted from TSR at the end of 1985, Mentzer left TSR as well and helped him to start New Infinities Productions Inc. (NIPI).  When this venture failed, Mentzer left the gaming industry, eventually becoming the manager of a bakery.  In 2008, he closed down this business and, two years later, announced he was returning to the gaming industry as a founding partner of a new publishing company, Eldritch Enterprises.
Answer: Frank Mentzer