a ship then new they built for him of mithril and of elven-glass with shining prow ; no shaven oar nor sail she bore on silver mast : the silmaril as lantern light and banner bright with living flame to gleam thereon by elbereth herself was set , who thither came and wings immortal made for him , and laid on him undying doom , to sail the shoreless skies and come behind the sun and light of moon .