"Return to Ashes" is the action theme of Mile High and Hostile Takeover (Chapter R-03 and R-04, respectively) from Metal Gear Rising: Revengeance. It's instrumental is also used in the Blade Wolf DLC during the Denver portion of Blade Wolf's VR training. The lyrics describe a flashback and how things worked to the past. It's a metaphor, "Return to Ashes" means "return to past", saying that if we continue down the same path, we will destroy ourselves, so it may also be due to the famous burial speech: ashes to ashes.