Niorun (Njörun) is a mysterious Norse figure about whom little is known, and some suggest may have been fictitious. She is listed as a goddess in a single source, and has been used as a kenning in some poetry, most notably Draum-Njörun or Dream-Niorun. This has led to the speculation she may have been a dream goddess.
It is said she chooses to live deep underground in Svartalfheim, where she is honoured and revered by both the Dark Elves and the Duergar (dwarves). Niorun’s hall is the only place where a traveller could claim sanctuary there, though it is also strange itself, and not altogether safe. It is filled with distorting mists of many colours, and one is often overcome by the compulsion to lay down and sleep.
Niorun herself can be seen as a veiled figure walking through the misty halls, her face almost never seen. If approached, she will speak in riddles and poetry, or say things that one later cannot remember.
In reality, Draum-Njörun was a moniker given to Lethe by Odin in the dream, when she danced around giving her true name. The information on her is sparse because she only existed within the dream itself, and was not truly a member of the Norse pantheon. Her realm in Svartalfheim was likely a reinterpretation of the Court of Hades, and her halls of sanctuary a reference to the pockets Lethe sometimes created in the dreamworld, and the ways she used them to react to Needs she sensed in others.
Obsessed as he was with knowledge and prophecy, it was inevitable that at some point Odin would encounter Lethe in the dreamworld.
She knew him as Grimnir (hooded or masked one). It’s unclear if Lethe knew his real identity, though she did also sometimes refer to him as Fjolnir (Wise One, concealer, “the One who is many”), suggesting she may not have been as ignorant as she made out. Likely, she just didn’t care.
When communication became difficult, Odin often communicated with her by way of one of his ravens, usually Muninn (memory).