1) Both monsters and heroes defend using the white shield

2) When attacking, throwing a black shield

I've been thinking about giving a special combat related rule to the barbarian, since out of the 4 hero's the only thing he has going for him is an extra body point.
3) Berserker rage: When attacking, if you kill a monster, and roll a black shield

My original idea was to have a berserker attack triggered when you roll all skulls (massive damage triggers the rage!) However, that approach would favor lower quality weapons, as they throw less dice and would have a greater chance to get all skulls. This didn't make sense thematically, a barbarian with a battle axe should go on the rampage more than if he was armed with a lowly dagger. With the black shield being the trigger, it won't activate every combat, and the better the weapon used, the greater chance you have to go berserk - barbarian feels a lot more cocky with better weapons. The rule encourages the barbarian player to charge into the thick of battle (as I think he would), so that there are plenty of adjacent targets to attack if he rages.
I welcome any and all comments. I haven't tested any of these rules out, they are just the results of my brainstorming in order to make combat a bit more interesting. I like the idea of combat potentially going back and forth with the counterattacks. I'm going to play my next couple of games using these new rules, and will report how it plays out.