Night of Naught

A place far westward from Middle-earth beyond the Great Sea that was consumed by perpetual darkness, and was also known as 'Evernight'. It was through this shadowy region that Eärendil voyaged on his quest to reach the Valar and plead for their aid. Elwing had carried a Silmaril to Eärendil's vessel Vingilot and, aided by the light of that shining Jewel, Eärendil was able to pass through the darkness and reach the shores of the Blessed Realm.

We have almost no detail about the Night of Naught, except for a line in Tolkien's unfinished index to The Lord of the Rings, where he defines it as a 'dark region south of Valinor' (quoted in The Lord of the Rings: A Reader's Companion). That might be taken to imply a part of the land of Aman (and indeed the description sounds like it might apply to Avathar, a dark land known to lie southward of Valinor). Bilbo Baggins' "Song of Eärendil", however, makes it plain that Eärendil sailed across this region on his way to Valinor, so it must have been at least partly an area of sea rather than land. In this respect it perhaps matches more closely with the Shadowy Seas created by the Valar to protect their realm.