Heavy.. and dark.. pretty much the darkest song from Opeth, it's no surprise that Mikael was in depression at that moment. Very particular song and I understand why it is underrated, lots of Opeth fans are not really into pure death metal and such brutal stuff. I mean, the whole ambiance in this song and the vocals on it are just heavier than anything else. And the long riffs, long and heavy riff in the middle of the song, that constantly repeats (and this is a good point for the song, actually), wow.
^ And yeah, for the idiot* who talked about "only death vocals", there are clean vocals at the end (my favorite part).
*take it as a joke.