A hobbits tale by Bilbo Baggins.' in the Return of the King movie at the very end after the ring is destroyed. 'Calling me there, I will go there, and back again.' This is a reference to Bilbo, as in when Sam says 'There and back again. 'In the dark I hear a call.' It says dark because it said there was the end of days. And we come to end of days.' This means that eventually the world will come to an end and the speaker will have to do something else. Then, when it says 'When the seas and mountains fall. In dreams they will see their loved ones again.
But when everything seems hopeless, in dreams there is still hope. 'We will walk in bitter rain' is ash from mount doom or other parts of Mordor. The fellowship sets out in winter, so that's why it says 'When the cold of winter comes' 'Starless night will cover day' as Sauron's power grows the shadow spreads across the land, covering the face of the sun.
