Question: "Duet" is the seventeenth episode of the third season of The CW television series, "The Flash", which aired on March 21, 2017, the  story begins at the end of the "Supergirl" episode ,"Star-Crossed" on March 20, 2017, which sees Kara Danvers / Supergirl (Benoist) being put in a coma by Music Meister, with who (Chris Wood), Lar Gand, and alternatively as Valor and M'Onel), is a fictional superhero appearing in American comic books published by DC Comics, commonly in association with the Legion of Super-Heroes, Superboy, and Superman, is primarily known as who?
Context: The Music Meister is a fictional character created by Mike Jelenic, appearing in "Mayhem of the Music Meister! ", an episode of the "" animated series, voiced by Neil Patrick Harris.  The character later appeared in the comic book sequel to the series, of the same name, published by DC Comics.  A separate character also known as the Music Meister was later developed for the live-action Arrowverse family of shows on The CW, portrayed by Darren Criss in "Supergirl" and "The Flash", adapted from the original version. "Supergirl" is an American television series developed by Greg Berlanti, Ali Adler, and Andrew Kreisberg based on the characters created by Jerry Siegel and Joe Shuster in the "Superman" franchise and Al Plastino and Otto Binder's character Supergirl (Kara Zor-El).  The series stars Melissa Benoist in the titular role of Kara Zor-El / Kara Danvers / Supergirl, as well as Mehcad Brooks, Chyler Leigh, Jeremy Jordan, David Harewood, and Calista Flockhart, with Chris Wood, and Floriana Lima joining in later seasons.  In addition to original characters, several other characters from DC Comics universe also appear throughout the series.  For its first season, "Supergirl" aired on CBS, before moving to The CW for its second season. "Invasion!"  is the third annual Arrowverse crossover event, crossing over episodes of the Arrowverse television series "The Flash", "Arrow" and "Legends of Tomorrow" on The CW, and is inspired by the 1989 comic miniseries "Invasion! ".  Events at the end of the "Supergirl" episode "Medusa" on November 28, 2016 marked the beginning of the crossover, which officially began on November 29 with "The Flash", continued on "Arrow" on November 30, and concluded on "Legends of Tomorrow" on December 1.  Each of the latter three episodes were titled "Invasion!" .  "Invasion!"  sees Barry Allen recruit Kara Danvers / Supergirl to his Earth to help his team, Oliver Queen and his team, and the Legends to defeat the alien race known as the Dominators. Linda Danvers, formerly known as "Supergirl", is a fictional comic book superhero appearing in books published by DC Comics.  Created by writer Peter David and artist Gary Frank, she debuted in "Supergirl" vol.4 #1 (September 1996).  She is not to be confused with Linda Lee Danvers, the secret identity used by the Kara Zor-El incarnation of Supergirl prior to the events of 1985's "Crisis on Infinite Earths". Superman is a fictional superhero appearing in American comic books published by DC Comics.  The character was created by writer Jerry Siegel and artist Joe Shuster, high school students living in Cleveland, Ohio, in 1933.  They sold Superman to Detective Comics, the future DC Comics, in 1938.  Superman debuted in "Action Comics" #1 (cover-dated June 1938) and subsequently appeared in various radio serials, newspaper strips, television programs, films, and video games.  With this success, Superman helped to create the superhero archetype and establish its primacy within the American comic book.  The character is also referred to by such epithets as the Big Blue Boy Scout, the Man of Steel, the Man of Tomorrow, and the Last Son of Krypton. "Duet" is the seventeenth episode of the third season of The CW television series "The Flash", which aired on March 21, 2017.  The episode was written by Aaron Helbing and Todd Helbing from a story by Greg Berlanti and Andrew Kreisberg, and directed by Dermott Daniel Downs.  The episode features a musical crossover with "Supergirl" and reunites Grant Gustin and Melissa Benoist with their former "Glee" co-star Darren Criss, who portrays the Music Meister.  Jesse L. Martin also reunites with Jeremy Jordan, whom he previously worked with in the 2012 musical film "Joyful Noise".  The story begins at the end of the "Supergirl" episode "Star-Crossed" on March 20, 2017, which sees Kara Danvers / Supergirl (Benoist) being put in a coma by Music Meister, with Mon-El (Chris Wood) and J'onn J'onzz / Martian Manhunter (David Harewood) bringing her to Earth-1 in hope that Team Flash can save her. Lar Gand, known primarily as Mon-El (and alternatively as Valor and M'Onel), is a fictional superhero appearing in American comic books published by DC Comics, commonly in association with the Legion of Super-Heroes, Superboy, and Superman.  The character has been reinterpreted over the years, but in all versions, he serves as a hero with abilities similar to those of Superman, sometimes serving as a substitute for him. Supergirl (also known as Cir-El or Cheryl Kent) is a fictional superhero appearing in American comic books published by DC Comics.  The character is best known as one of the characters to have assumed the mantle of Supergirl.  Created by writer Steven Seagle and artist Scott McDaniel, she first appeared in "Superman the 10 Cent Adventure" #1 (2003) as the alleged daughter of Superman.  She is later found to be a human girl who was genetically altered by the villain Brainiac to appear Kryptonian.  The character dies thwarting a plot involving Brainiac 13. " Superman" (vol.  2) #200 implies that when the timeline realigned itself, Cir-El was erased from existence. Superboy (also known as Kon-El or Conner Kent) is a fictional superhero appearing in American comic books published by DC Comics.  A modern variation on the original Superboy, the character first appeared as Superboy in "Adventures of Superman" #500 (June 1993), and was created by writer Karl Kesel and artist Tom Grummett. Supergirl is a fictional superhero appearing in American comic books published by DC Comics.  The character was created by writer Otto Binder and designed by artist Al Plastino.  Supergirl first appeared in a story published in "Action Comics" #252 (May 1959) titled "The Supergirl from Krypton".
Answer: Mon-El