One of the most talented hip-hop production duos working right now is Blue Sky Black Death, a pair of dudes from the West Coast who make dark, brooding anthems, working largely with underground heroes like Nacho Picasso and Deniro Farrar. They've teamed up with the duo SAS, who helped them recruit the New York legends P.A.P.I. (N.O.R.E.) for "Valley of Kings," their first single from their upcoming joint project Celestial. Stream it below, and head over to BSBD's Bandcamp for more goodies.