[1] Spirits are thought to travel between worlds or layers of existence in such traditions, usually along an axis such as a giant tree, a tent pole, a river, a rope or mountains.
In many cases such as in Persian, Greek, Germanic, Celtic, Slavic and Indic mythologies, a river had to be crossed to allow entrance to it, and it is usually an old man that would transport the soul across the water.
A similar myth is that of Yama, the ruler of Hell in Hindu mythology, who watches the gates of underworld with his two four-eyed dogs.
In Celtic oral tradition, the Otherworld is often portrayed as an island out to the west, and even appears on some maps of Ireland during the medieval era.
[2] The Early Slavs believed in a mythical place where birds flew for the winter and souls went after death; this realm was often identified with paradise and is called Vyraj.
J. R. R. Tolkien drew upon the Sir Orfeo text, which depicts a journey to the Otherworld, as inspiration for the Mirkwood Elves of The Hobbit.
[15] C. S. Lewis also drew upon the tropes of the Celtic Otherworld in his creation of The Chronicles of Narnia, which depicts the journey from this world to another.
Andoni Cossio (2021) Sir Orfeo as the Source for the Medieval Romance Topoi of Abduction and Otherworld Rampant within The Hobbit’s Mirkwood, ANQ: A Quarterly Journal of Short Articles, Notes and Reviews, DOI: 10.1080/0895769X.2021.1967105