Luthien was the most beautiful of all the Children of Illuvitar. Blue was her raiment as the unclouded heaven, but her eyes were grey as the starlit evening; her mantle was sewn with golden flowers, but her hair was dark as the twilight. As the light upon the leaves of trees, as the voice of clear waters, as the stars upon the leaves of trees, as the voice of clear waters, as the stars above the mists of the world, such was her glory and her loveliness; and in her face was a shining light...and the song of Luthien released the bonds of winter and the frozen waters spoke, and flowers sprang from the cold earth where her feet had passed.

 The Silmarillion