Ælfwine

Ælfwine (originally named Ottor Wæfre, and by the Elves Eriol, and also, less commonly, Angol, Lúthien, and as Ælfwine of England/Engaland) was a mariner (or perhaps mariners) who first appear in the early versions of Tolkien's mythology, providing via narration the main story-lines for both volumes of The Book of Lost Tales. He (or those going by the name) continued to be an editor and 'presenter' of material into many of the later First Age Histories and Annals as well as appearing in most of the books in The History of Middle-earth. He is reintroduced in part in Beren and Lúthien (2017))

He was the first to find the Straight Road and visit Tol Eressëa after many millennia. His character acts as a catalyst for the telling of the early history of Middle-earth during story-telling sessions in and around the Cottage of Lost Play where he was a guest of the elves Lindo, his wife Vairë, and Gilfanon on the Isle of Tol Eressëa.

Biography
Ælfwine was a Man who lived (c. 500 - 1001 A.D.) in the lands East of the North Sea. He lived much of his life on the waters. He lived period preceding the Anglo-Saxon invasions of Britain, and later as an Englishman of the Anglo-Saxon period' who dwelt in the South-west (of England), the kin of Ing, King of Luthany. The Ingwaiwar ('sons of Ing') (Inguaeones) were the Anglo-Saxon invaders of Britain (and connected to Ingwë) and his ancestors, who descended from Ermon and Elmir, the first Men.

In early stories, his father was named Eoh who was slain by his brother Beorn. Both were the sons of Heden, and like many heroes of Northern legend traced his ancestry to the god Wóden. In other versions of the tale, he is man of 11th century Wessex in Luthany, as a child he was a great lover of the elves, especially of the shoreland Elves that still lingered in the land, and always sought for Tol Eressea where the fairies were said to have retired. He has learned ancient tongue of English and Elfin speeches. His mother and father were slain by sea-pirates and he was made captive. He escapes and meets the Ancient Mariner...

Ottor would come to settle on the island of Heligoland in the North sea, and he wedded a woman named Cwén; they had two sons 'named after his father' Hengest and Horsa 'to avenge Eoh', and around 500 A.D. they took part in the invasion of Britain.

Then sea-longing gripped Ottor: he was a son of Eärendel, born under his beam. If a beam from Eärendel fall on a child new-born he becomes 'a child of Eärendel' and a wanderer. In later versions it is descried that he loved the sign of Orion, and made the sign, hence the fairies called him Lúthien (Wanderer).

After the death of his wife, Ottor left his young children. Hengest and Horsa went to avenge Eoh and became great Chieftains; but Ottor set out to sea (from England in some of the later versions), and find, Tol Eressëa (uncú þa holm, ‘the unknown island’ or seo unwemmede íeg), whither most of the unfaded Elves have retired from noise, war, and clamour of Men. In later stories, the location he learned from the Ancient Mariner...and/or he is driven there by the Normans.

Waking up on the island, he met elves and other fairy folk and from them learned stories of ancient times. he was given the names Ælfwine (Elf-friend') and Eriol ('One Who Dreams Alone'), and he adopted the name Angol, and that he was named by the Gnomes (Noldor) 'after the regions of his home' (the region Angol is also known as Eriollo to the Noldor, and relates to the Danish peninsula between Flensburg fjord and the river Schei, south of the modern Danish Frontier, no great distance to the island of Heligoland). ...or Lúthien (man of Luthany/'wanderer', Luthany the land they called 'friend' and 'friendship' Eldaros or Ælfhâm).

Depending on evolution of the story, he either sailed from England out into the Atlantic Ocean, or he sailed to an island that would later become England in the future. Eriol came to Tol Eressëa roughly in the time after the Fall of Gondolin and the march of the Elves of Kôr into the Great Lands for the defeat of Melko, when the Elves who had taken part in it had returned over the sea to dwell in Tol Eressëa; but before the time of the ‘Faring Forth’ and the removal of Tol Eressëa to the geographical position of England (an idea that would be lost in later writings).

Luthien Aelfwine drinks of the Limpë (much like Ing before him), but thirsted for his home, and went back to Luthany, and then thirsted unquenchably for the Elves, and went back to Tavrobel the Old and dwelt at the House of the Hundred Chimneys (where grows still the child of the child of the Pine of Balawryn) where he wrote the Golden Book: The Book of Lost Tales and the History of the Elves of Luthany: The Golden Book of Tavrobel.

A later source, suggests yet another short background that AElfwine  of  England in (c.900 A.D.),  called by  the Elves  Eriol, was blown off-course  west  from  Ireland, eventually  came upon  the 'Straight Road' and found Tol Eressea the Lonely Isle. He  brought  back copies  and translations  of many  works.

Etymology
The name Ælfwine simply means "Elf-friend", and is the Old English equivalent of Elendil. The name Alvin is a modern descendant. It is possibly intended as a cognate of Alboin.

Behind the scenes
Although there is little evidence of this storyline in the published version of The Silmarillion, some of the later writings of Tolkien indicate that he didn't fully abandon the idea. However, although Ælfwine is still referred to in some post-Lord of the Rings writings, Tolkien ultimately changed the intended framework of The Silmarillion from the tale of Ælfwine to one based around Bilbo Baggins' ''Translations from the Elvish books of "Elvish lore". However, the idea of stories coming from different 'voices' Hobbits, Elves, Man, and others is not completely dropped, leaving that kernel that in some distant 'future' Ælfwine also encountered story tellers and materials by other writers and released his own adaptations of the stories (as noted in Beren and Lúthien (2017) allowing for the 'discrepancies' between accounts to arise.''

Ælfwine is also given as the author of the various translations in Old English that appear in The History of Middle-earth series. A minor discrepancy is that whereas Ælfwine is described as hailing from the north-west of England, his Old English texts are in the Mercian dialect, which was Tolkien's favourite. He also referenced in the The Teachings of Pengalod.

Ælfwine was intended to be the introductory voice adapting Middle-earth, and a number of other legends into his greater 'new mythology for England' concept. Hence his son Hengist also appears across other stories. This was a matter to which J.R.R. Tolkien gave much time and thought; he lectured on it at Oxford and developed certain original theories, especially in connection with the appearance of Hengest in Beowulf.

It's not necessarily that Eriol life extended some 300-500 years, the each of the given dates (500, 900, 1th century) are simply be revisions of moving the character and his background several centuries forward or back (as he was thinking about the character's history). However, its worth noting that in the Lost Tales Eriol does drink a draught (Limpë) which is said could extend his life to that much like the elves. So the idea that could have lived several hundred years is already tied into concepts Tolkien was developing.

Likewise certain elements of "Ing" (who comes to be known as Ingwë, sharing ) and his own backstory seem to share elements of the early Ottor story (who also traveled to Tol Eressea, and lived there drinking of the Limpe), as such making it possible there were multiple Aethwines.("Elf-friends") from different eras.