I'm having some difficulty following who is talking. I originally thought that Luke was in a cave on Tatooine, mentally communing with Yoda, but the moss and the light years make it sound like he is back on Dagobah talking directly to Yoda. I assume that he is also hearing Vader's voice in his head while this is happening.
It's a good start, but would be easier to follow if we were told who was speaking.