Sellic Spell (] , an Old English phrase meaning "wondrous tale" and taken from the poem "Beowulf") is a short prose text available in Modern and Old English redactions, written by J.R.R. Tolkien in a creative attempt to reconstruct the folktale underlying the narrative in the first two thousand lines of the Old English poem "Beowulf".
 Among other things, it seeks to clarify and integrate a number of narrative strands in the Anglo-Saxon poem.
 The resulting text is a loose variant of the "Skilful Companions" type of folktale, in which each of several characters (two or three in Tolkien's text, depending on the redaction) has a valuable but specific skill.
 Unlike in folktales of that type, however, the skills of Tolkien's characters do not supplement each other in the resolution of the narrative problem.
 Tolkien's recasting of the material also incorporates the sluggish youth motif and the abandonment of the hero at the waterfall, both elements found in the analogous Old Icelandic "Grettis saga".
 The suggestion that a waterfall like that of "Grettis saga" was part of the original setting of the pool of monsters in "Beowulf" was made by W.W. Lawrence in 1912.
Elu Thingol (Y.T. ≥1050–Y.S. 502; died aged c.4814) is a fictional character in J.R.R. Tolkien's Middle-earth legendarium.
 He appears in "The Silmarillion", "The Lays of Beleriand" and "Children of Húrin" as well as in numerous stories in the many volumes of "The History of Middle-earth".
 He is notably a major character in many of the stories about the First Age of Tolkien's Middle-earth and he is an essential part of the ancestral backgrounding of the romance between Aragorn and Arwen in "The Lord of the Rings".
Sauron is a fictional character from J.R.R. Tolkien's Middle-earth fantasy writings, and the title of one of the three games in the board game "Middle Earth" based on the character.
Glorfindel () is a fictional character in J.R.R. Tolkien's Middle-earth legendarium.
 He is introduced in various material relating to the First Age of Middle-earth, including "The Silmarillion".
 The name is also used for a character in "The Lord of the Rings", which takes place in Middle-earth's Third Age.
 In late writings, Tolkien works out how the two characters were one and the same, though this is not evident from the published versions of "The Silmarillion" and "The Lord of the Rings".
Gandalf is a fictional character and one of the protagonists in J. R. R. Tolkien's novels "The Hobbit" and "The Lord of the Rings".
 He is a wizard, member of the "Istari" order, as well as leader of the Fellowship of the Ring and the army of the West.
 In "The Lord of the Rings", he is initially known as Gandalf the Grey, but returns from death as Gandalf the White.
Celeborn (pronounced with a hard "c" as in "cat"; ) is a fictional character in J.R.R. Tolkien's Middle-earth legendarium.
 Celeborn is an Elf, and the husband of Galadriel.
 He appears in "The Lord of the Rings" as the Lord of the Galadhrim, and co-ruler along with Galadriel of Lothlórien.
 He was the father of Celebrían (the wife of Elrond), and thus the grandfather of Arwen Evenstar and her older brothers Elladan and Elrohir.
 He was also a kinsman of the First Age Elven King Thingol.
 "Celeborn" means "(tall) silver tree" in Tolkien's invented language of Sindarin.
Ian McKellen (born 25 May 1939) is an English stage and screen actor.
 He is the recipient of six Laurence Olivier Awards, a Tony Award, a Golden Globe Award, two Academy Award nominations, four BAFTA nominations and five Emmy Award nominations.
 McKellen's work spans genres ranging from Shakespearean and modern theatre to popular fantasy and science fiction.
 His notable film roles include Gandalf in "The Lord of the Rings" and "The Hobbit" trilogies, Magneto in the "X-Men" films, Sir Leigh Teabing in "The Da Vinci Code" (2006), Sherlock Holmes in "Mr. Holmes" (2015) and Cogsworth in "Beauty and the Beast" (2017).
Eru Ilúvatar is a fictional character in J.R.R. Tolkien's Middle-earth legendarium.
 He is introduced in "The Silmarillion" as the supreme being of the universe, creator of all existence.
 In Tolkien's invented Elvish language Quenya, "Eru" means "The One", or "He that is Alone" and "Ilúvatar" signifies "Father of All".
 The names appear in Tolkien's work both in isolation and paired ("Eru Ilúvatar").
Tauriel is a fictional character from Peter Jackson's feature film adaptation of J.R.R. Tolkien's "The Hobbit".
 The character does not appear in the original book, but was created by Peter Jackson, Philippa Boyens and Fran Walsh as an expansion of material adapted from the book, and first appears in the second and third films in that trilogy, "" and "".
 She is a Woodland Elf whose name has been translated as "Daughter of the forest", and is the head of the Mirkwood Elven guard.
 She is played by Canadian actress Evangeline Lilly, who was nominated for several awards for her performance in "The Desolation of Smaug", with some of the stunt work performed by Australian stuntwoman Ingrid Kleinig.
Túrin Turambar (pronounced ) is a fictional character in J. R. R. Tolkien's legendarium. "
"Turambar and the Foalókë"", begun in 1917, is the first appearance of Túrin in the legendarium.
 J.R.R. Tolkien consciously based the story on the medieval tale of Kullervo in the Finnish mythological poem "Kalevala", saying that it was "an attempt to reorganize...the tale of Kullervo the hapless, into a form of my own".
 Also called ""The Tale of Grief"", ""Narn i Chîn Húrin"", commonly called "The Narn", it tells of the tragic fates of the children of Húrin, namely his son Túrin (Turambar) and his daughter Nienor.
 Excerpts of the story were published before, in "The Silmarillion" (prose), "Unfinished Tales" (prose), "The Book of Lost Tales" Part II (prose), "The Lays of Beleriand" (verse in alliterative long-lines) and most recently in 1994 in "The War of the Jewels" (prose), the latter three part of "The History of Middle-earth" series.

Question: Gandalf is a fictional character played by English stage and screen actor, Ian McKellen, in what two J.R.R. Tolkien novels turned films?
Answer: "The Hobbit" and "The Lord of the Rings"