Probably answered before, couldnt find it though:
rtl rulebook page 23 "In a Gold campaign, a hero can upgrade as many of his black and silver dice as he wants, but only a maximum of one silver die to a gold die."
It seems like it is possible to upgrade all 5 traitdices to gold, yet the last part confuses me(was it meant to be a diamonddice....
). Can the heroes upgrade all silver dices(trait) to gold dices, or can they only upgrade one of them?