Diablo III: Reaper of Souls is the first expansion to Diablo III.
It was announced at Gamescom, August 21st 2013, and continues the story from Diablo III after a brief period of peace.
"The Prime Evil lies defeated, confined to its Black prison by the Nephalem, in the hope of an age of peace and prosperity. And yet, when Angels have fallen, so begins the end of all things."