Evernight

We have only the vaguest description of Evernight, so we cannot be sure where its boundaries lay. Hyarmentir was a peak that lay to the south of Valinor, which therefore places it in the same general region as Evernight, and so we might reasonably imagine it as lying within that area, though it is impossible to state this with certainty.

The reason that Evernight was associated with endless darkness is not explained. It presumably lay eastward of the Mountains of Defence, and would therefore have been shadowed from the Light of the Trees during the time they shone in Valinor. That offers a possible explanation for the name's origins, though when Eärendil passed through this region the Trees were long gone and the Sun would have shone down on the land, so 'Evernight' seems an odd description. We know that Ungoliant had dwelt in the southern lands in ages past, and webbed the mountains in darkness, so perhaps this offers an alternative reading of the name's meaning.