This was already in the title but I'm going to stress it again here: Blade of the Ruined King is not, strictly speaking, an instrumental. I know ominous chanting when I hear it and this song is chock-full of the stuff. The actual language of the chanting could be anything from Latin to gibberish, but I KNOW I heard the word "Noxus" in the song at least twice.
The problem is that whenever I try to look up the lyrics, multiple lyrics websites "helpfully" inform me that the song is an instrumental. Does anyone know if Riot ever published the lyrics?