Question: What is the artefact which corrupted J.R.R. Tolkien's fictional character, Smeagol?

Context paragraphs:
Glorfindel: 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".

Celeborn: 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.

Tauriel: 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.

Eru Ilúvatar: 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").

Thingol: 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".

Amandil: Amandil is a fictional character from J.R.R. Tolkien's Middle-earth legendarium.  Amandil was a Lord of Andúnië, succeeding his father Númendil upon his death.  Amandil is most noted for being the father of Elendil, founder of the Númenórean Realms in Exile.

Gollum: Gollum is a fictional character from J. R. R. Tolkien's legendarium.  He was introduced in the 1937 fantasy novel "The Hobbit", and became an important supporting character in its sequel, "The Lord of the Rings".  Gollum was a Stoor Hobbit of the River-folk, who lived near the Gladden Fields.  Originally known as Sméagol, he was corrupted by the One Ring and later named Gollum after his habit of making "a horrible swallowing noise in his throat".

Túrin Turambar: 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.

One Ring: The One Ring is an artefact that appears as the central plot element in J. R. R. Tolkien's "The Lord of the Rings" (1954–55).  It is described in an earlier story, "The Hobbit" (1937), as a magic ring of invisibility.  In the sequel, "The Lord of the Rings", Tolkien ascribes to the Ring a darker character, with malevolent power going far beyond conferring invisibility: it was created by Sauron the Dark Lord as part of his design to win domination over Middle-earth.  "The Lord of the Rings" concerns the quest to destroy the Ring to keep Sauron from fulfilling his design.

Sauron (disambiguation): 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.

Supporting paragraphs: Gollum One Ring
Answer: One Ring