Song used is ‘Evelyn Evelyn’ by the band of the same name.
This is kinda old and I’m probably never gonna finish it.
Ok, let’s see how much of this I can explain. Curumo and Mairon used to be co-dependent on one another, in a sense, and by that, I mean even before Mairon was evil he was always sort of “empty”, thus he ever needed someone to give him an opinion. Curumo used to be a good opposite as one who generally holds strong opinions in the realm of “if you don’t do this, you aren’t very wise.” Curumo’s was like the brain and Mairon was like the heart. Though when Mairon found Melkor, he had a new mind to rely on and thus, no longer needed Curumo.
So the concept of the video is that by the time Curumo goes to middle earth to lead the efforts against Sauron, he finds his “heart” again, but of course it’s tainted, and so he he becomes tainted with it.
Alt title for this: The Two Towers