I bought the backpack for Barbarian while right now I am a Sorcerer, now my item is useless since I cannot activate it. I put so many hours in this, is there a sollution? I thought you could buy any item you would like and use it for next season as well.
You can activate it, just create a Barb, skip the campaign at creation, and go to your chest (but put it first in your chest with your sorc).
It will take you 2mn max and you will have activated the cosmetics for any Barb you create. Cosmetics are usable in any coming seasons (it’s shared across your account), but not items FYI. So any brew you buy will go to Eternal at the end of the season, not to the next season.