So Graz chooses a target he is going to attack. Lets say Lil' Ned but Moira is there too. He rolls the dice vs. Ned including Ned's defense dice.
G&P scores a BAM which reads "BAM: must target a different here in this zone" what happens next?
Does he use those attack/defense dice and direct the result against moira?
do I pick up Ned's defense dice and re-roll Moira's?
Do I reroll the whole round of combat vs. Moira?
Maybe I am being dense but what is this ability supposed to do?
New South Wales
The full ability text is:
"When they Attack, if there's more than 1 Hereo in the Zone, roll 1 red die: Bam: Must target a different Hero in this Zone instead."
So, as they are Melee only, if they have multiple heroes in their Zone when they activate (normally or for Counter-Attack), they first roll a red die. If that die has a Bam, they choose a different Hero to Attack. They then resolve the Attack against the Hero.
I think the confusion has come because you were assuming this to be a standard Enchantment that activates during the attack, which is incorrect. It doesn't have the Attack or Defense Combat types, so it is only applying to that single die which is rolled before the Attack.