The legendarium's origins reach back to 1914, when Tolkien began writing poems and story sketches, drawing maps, and inventing languages and names as a private project to create a mythology for England.
The Lord of the Rings occasionally alludes to figures and events from the legendarium to create an impression of depth, but such ancient tales are depicted as being remembered by few until the story makes them relevant.
Tolkien's son Christopher chose portions of his late father's vast collection of unpublished material and shaped them into The Silmarillion (1977), a semi-chronological and semi-complete narrative of the mythical world and its origins.
[T 1] Tolkien described his works as a "legendarium" in four letters from 1951 to 1955, a period in which he was attempting to have his unfinished Silmarillion published alongside the more complete The Lord of the Rings.
[2][3][4] Christopher Tolkien's introduction to The History of Middle-earth series talks about the "primary 'legendarium'", for the core episodes and themes of The Silmarillion which were not abandoned in his father's constant redrafting of the work.
[7] He intended his stories to become a mythology that would explain the origins of English history and culture,[T 10] and to provide the necessary "historical" background for his invented Elvish languages.
Much of this early work was written while Tolkien, then a British officer returned from France during World War I, was in hospital and on sick leave.
[T 15] From the "Sketch" Tolkien developed a fuller narrative version of The Silmarillion called Quenta Noldorinwa[T 16] (also included in Volume IV).
[8] There is no such framework in the published version of The Silmarillion, but the Narn i Hîn Húrin is introduced with the note "Here begins that tale which Ǽlfwine made from the Húrinien.
[T 21] Writing The Lord of the Rings during the 1940s, Tolkien was attempting to address the dilemma of creating a narrative consistent with a "sequel" of the published The Hobbit and a desire to present a more comprehensive view of its large unpublished background.
[11] With the success of The Lord of the Rings, Tolkien in the late 1950s returned to the Silmarillion, planning to revise the material of his legendarium into a form "fit for publication", a task which kept him occupied until his death in 1973, without attaining a completed state.
[T 22] The scholar Verlyn Flieger writes that Tolkien thought of his legendarium as a presented collection, with a frame story that changed over the years, first with an Ælfwine-type character who translates the "Golden Book" of the sages Rumil or Pengoloð; later, having the Hobbit Bilbo Baggins collect the stories into the Red Book of Westmarch, translating mythological Elvish documents in Rivendell.
[13] The scholar Gergely Nagy observes that Tolkien "thought of his works as texts within the fictional world" (his emphasis), and that the overlapping of different and sometimes contradictory accounts was central to his desired effect.
Nagy notes that Tolkien went so far as to create facsimile pages from the Dwarves' Book of Mazarbul that is found by the Fellowship in Moria.