do characters from all campaigns share gold?

if i use prophecies and put gold in the bank, can nightfall access that gold?

That is correct. The Xunlai chest is shared by all characters on the same account.

ty very much

Not only that, but, if you plan to start a new character (any campaign) it's normal to put mats, gold, weapons, etc, into storage for the new character to use as soon as they can access storage.