The 9:52 long track immediately blasts you off your feet with a ethereally heavy series of riffs and Aaron Turner's rough vocals. Keeping it interesting, the structure continues to evolve, and drifts downward into a more dreamy movement which stays dense and builds the tension for the following verses. About halfway in, the song reaches the first climax that (I think) embodies the "Threshold" in the song title. After which, it moves into a more contemplative section, smoothing out the turmoil and tension brought on by the first half, while building its own. Beautifully, it succeeds in building yet another crescendo, only to end in free fall, with guitar and bass fantastically accenting the mood. The bass in this song is truly something to behold, wavering and powerful in its tone.
What I like about this song reflects on why I like Isis' music in general: it's complex, atmospheric, emotional, intricate, and smart. It truly is "thinking man's metal." Isis is all about themes and atmospheres, emotions and vibes, rather than clear ideas and lyrics. It's visceral, raw, and transcendent. And in some ways, I think this song embodies everything that makes them great.