Moriquendi - Elves of the Darkness' or Dark Elves
But since it ends us with I again, (I'm sorry, could not think up anything without I on its end
), I suggest we can use the ending S of Common Speach translation)
Or, Besides answering, I propose a modification too - if the ending letter is the 'hard one' (say, i or q), let it be allowed to use the last letter of the translation, eh?