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.
PTR 2.6.10 Preview Blog
https://us.diablo3.com/en/blog/23529004
woohoo helltooth angry chicken for the win
Also from the US blog regarding season 22:
Could be a cool season.
The fourth slot seems pretty good, will give us many possibilities. Many ppl will reach the gr 150.