White Host, Green Room (By Joren ‘Tensei’ de Bruin) is one of the album bonus tracks (and thus only available if you purchase the album). It’s a jazzy, slow-paced piece. I’m not a big fan of it: don’t hate it, but it’s not really on my playlist. There’s one thing about it that does interest me: the intro.
The song begins with a fuzzy medley of four songs. The first two are Terezi Owns (on this album) and Cascade (on Volume 8: this sneak peek was released well before Cascade came out, mind you). The last song is Black Rose / Green Sun.
There’s an excerpt from one other song in the middle, starting at the ten second mark: epic choir chanting and heavy, distorted electric guitar. It sounds like a ‘final boss fight’ song. Yet the track that this little snippet belongs to hasn’t been released in any official way. So, what’s it all about?

Turns out it’s an unfinished track called 'The King in Red’. Tensei made a blog post about it here, and you can listen to the work-in-progress version of the song there.