According to Snorri Sturluson's Gylfaginning, Gjöll originates from the wellspring Hvergelmir in Niflheim, flowing through Ginnungagap, and thence into the worlds of existence.
Within the Norse mythology, the dead must cross the Gjallarbrú, the bridge over Gjöll, to reach Hel.
The bridge, which was guarded by Móðguðr, was crossed by Hermóðr during his quest to retrieve Baldr from the land of the dead.
In the following chapter, these are called the Élivágar and are said to have flowed in Ginnungagap in primordial times.
[2] Gjöll has a parallel with similar mythological rivers from Indo-European cultures such as the Greek Styx and the Hindu Vaitarani.