You're probably playing through Diablo III: Reaper of Souls and thinking about what comes next for Sanctuary. Turns out it's a 2D mobile tapping adventure called Happy Reaper.
Battle.net has first details on Malthael, the Angel of Death's new story. Make your reaper happy by plowing through hapless nephalem with Malthael's appropriately-titled Death Laser of Doom. It's called that because it's a death laser that kills!
If you don't want to wait for Happy Reaper to come to mobile, you can play it right now.