The Ghosts in the Dark Achievement has been in-game since 2010. Shawn and I didn’t discover it until 2015. The interesting thing about this Achievement is that it involves a Demon Hunter – but is not part of the Legion expansion (which is in beta at the time I am writing this blog).
The Ghosts in the Dark Achievement is for Alliance characters, only. There is a separate one (called Joy Ride) for Horde characters. Shawn and I were playing two Dwarf characters together, so we did the Alliance version.
The screenshots you see in this blog were taken on August 20, 2015.