Descendents of The Lost by picabone99
Harry/Glorfindel
https://archiveofourown.org/works/1113746#main
It's been a while since I read this story and it is still a great blending of LOTR and HP. Harry goes through the veil with Sirius and they are transformed into elves of a corresponding age. Which would be toddler and tween and a new adventure starts. They end up in Rivendell and the story explores what happens around and behind the movie. I wish the story had gone into more detail about the courtship between Harry and Glorfindel there are too many jumps. However the story is well written the action scenes are thrilling and you get a better look at lives of everyday elves.
