Rewards: Two unique new rewards, a portrait frame, and a pet will be granted to players who complete the Season 22 Guardian Journey.
Kanai’s Cube: Additionally, the Kanai’s Cube will
have a fourth slot this season. This fourth slot will have the choices
of the first 3 slots but will not stack with any of them. The intent is
to provide players with creative flexibility to their character builds.
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Also from the US blog regarding season 22:
Could be a cool season.