Bronze Bars are items you buy to bank your gold. * Warning! You will only receive 70% refund if you decide to sell them back. Here is a link to the banner guide: The Official Banner Guide In the mage you enchant your equipment. You must unlock Caslte Level 3.
Originally put in the game as a end eb bonus not as a bank. Some ebs still drop them like the Motos TGL dragon series i believe. Pretty sure they added bronze bars to the game when it was right after they got rid of the "rare hidden chest" of gold that dropped 5-15bil after the completion of Fod and cotd back in the day. Those were huge at the time! Making 10-20bil in one day was hard work back then. All pots have the same return on investment when selling, so added nothing new to the game in that element. Could have banked in atk/spy offensive pots to do the same exact thing. But ya now all they are used for is for upgrading banners. Devs said something about adding a blacksmith, but i think that idea was scrapped by them as it seems like forever ago they mentioned it with no follow up on it. Doubt they will do anything new with bronze bars. Wish tier 11 ebs would drop them though.