Disclaimer: Nothing Tolkien originally created belongs to me.
This is a dream I must have had right after reading Tolkien's 1917 version of "The Tale of Tinuviel". I'd been thinking about Tinuviel's stay in the beech tree in that version of the story, and how, unlike in the "Silmarillion" version, it took a dream sent by the Valar to actually get her back on her way to saving Beren. I was pondering how the early Tinuviel seemed less dedicated and more easily distracted than the later one.
Well, in this dream, I was reading the same version of the story, but it was extremely different. In the dream version, Luthien, apparently, was even more distractible; she had ADD or something. The dream ended before she finally got to Tevildo's castle, because she took so many detours that her journey took forever. In the one I remember, Luthien was hurrying on her way again, when suddenly, a herd of rainbow unicorns galloped past her. Immediately, she cried, "Hey, look! Rainbow unicorns!" and turned right around and ran after them. The dream ended there, so I never got to learn about Luthien's adventures—if she had any—with the unicorns.