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
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.