Blizzard announces that Season 22 is now live in Diablo III, bringing new challenges to their action/RPG sequel. This previous post is updated to reflect the launch, offering updated patch notes. Here's an overview of the central theme of the new season:

New Season Theme
Nephalem, do you feel it? All around, the shadows of the past linger, waiting for an opportunity to channel their power once more and aid you against the minions of hell. Will you stand up to the challenge and accept the aid of these erstwhile spirits? The Shades of the Nephalem await....

During Season 22, activating a Shrine or Pylon will spawn in a shadow clone of your class. The clone's power will scale with your character and will last for one minute or until death.

Shadow Clones in action
In addition, for the duration of Season 22, Kanai's Cube will have a fourth slot. You will have the option to choose any power for this one, but it won't stack with powers from other slots.