Originally done for the cover of The Book of Lost Tales 2, Grafton Books, 1992
More info on the subject matter https://lotr.fandom.com/wiki/Door_of_Night
But Morgoth himself the Valar thrust through the Door of Night beyond the Walls of the World, into the Timeless Void; and a guard is set forever on those walls, and Eärendil keeps watch upon the ramparts of the sky.
yeah now this is exactly why i like portal art
i love the sense of hope implied by the light and the golden-white ship streaming into the dark of the night-time side