I haven’t watched it all yet, but it’s worth posting. Bungie uploaded another developer commentary, this time of Deep Stone Crypt.

I jumped in and out of this stream while it was live. Some very interesting stuff in here, as well as behind the scenes "Graybox" footage. There may be more than I saw, but I can say there is some Graybox footage of the Final Boss of the Raid.

For those of you who prefer reading about this kind of stuff, Bungie has made something for you. It's (expertly) called Tales From the (Deep Stone) Crypt. No "Graybox" images here, but the little concept art in it is pretty cool, of course.