why barbarian cannot use ashbringer in kanais cube but it drops for him?
The Corrupted Ashbringer is one of the few legendaries that have a legendary power which can not be extracted. It has nothing to do with the character class one uses, it’s more about overall balancing.
I thought the reason that it cannot be extracted is because of the fact that the sword visually transforms when it’s power activates, which is a unique mechanic to that sword and so cannot be applied to other weapons.
Also it’s some kind of easter egg / reference item to something in World of Warcraft i think, so that might have something to do with it not being extractable.