There has been some considerable discussion in the Hit Points and Damage thread about whether armour should reduce the damage you take from energy attacks such as fireball. I am going to summarise those arguments here. You can vote in the poll at the bottom of the page.
In HD&D Armour Class works like damage reduction did in third edition. You subtract the armour class value from the damage dealt before applying the damage to your foe. So if you strike an opponent for 20 damage, and they are wearing Plate Armour (AC 9), then they only take 11 points of damage.
Option One: Armour doesn’t defend against energy attacks
My intention was that armour class should only defend against physical attacks from weapons and other solid objects. The game already has Energy Resistance, which works in a similar way but protects against energy attacks such as Fire, Electricity, Thunder, Radiance and so on.
If we allow armour to protect you against a fireball as well as sword swing then we are in danger of making armour too good in the context of the game. It also weakens energy resistance. A tiefling starts with Fire Resistance as one of his class traits. What’s the point if anyone can also get fire resistance by putting on some chain-mail?
D&D has never allowed armour to do this in the past, and I don’t see why we need to do it now. It just seems unnecessary, and will cause too many mechanical issues just for the sake of closing a loop hole that isn’t really there.
Option Two: Amour must defend against energy resistance!
The counter argument is that armour should defend against energy attacks, because in the real world that is exactly what would happen. HD&D strives for verisimilitude, well here is a big fat example that HD&D cannot afford to ignore.
The instantaneous burst from a fireball won’t penetrate armour. Electricity will arc around armoured foes and damage them less. These are scientific facts, and the game should accomodate them.
So there are the options. If you’re still not clear what all this is about, go back and have a read of the aforementioned discussions. Get informed and then vote. Your vote counts, you know!