This is my favorite riff of the song. Melodically, it somewhat shadows the very 1st riff we did. However, it sounds much more aggressive here, especially with the accompanying drum parts.
Be sure to keep your palm muting tight and your picking solid. Also, be careful with the descending pattern at the end of bar 18. It requires some fast arm and finger movement. As I've said before, just practice slowly and take your time.
Lastly, when you play this part along with the backing track, do your best to focus on what you're actually playing, and not necessarily what the other instruments are doing. This section is pretty busy with the drums and harmonized guitar, so it might be easy to get distracted, but make sure you stay focused.
Speaking of the backing track, head on over to the next page for the backing track! :)