I had been toying with an idea recently about changing the nature of how Armor would work. I reasoned that having Armor's damage reduction (DR) apply to every attack could slow down the game by adding to the number of rolls on any given turn in combat. Having magical weapons bypass non-magical armor would ameliorate the problem to a degree while simultaneously making magic items more awesome (something I'd like to do and move away from Christmas Tree effects.) However, since the PC's are likely the ones to be packing magical heat all this does is eliminate the rolling for enemies who, when aren't humanoid, frequently do not wear armor.
I came up with another idea based on realism which is so often sought after by out of touch GM's and simultaneously reviled by players just looking to have fun. Well hopefully this idea doesn't fall into that category. See I considering having armor apply only to when your Wounds take damage. [Wounds are discussed here] Since armor exists to protect those valuable squishy organs and wounds are a reflection of how close you are to dying it goes to reason that armor should invariable be protecting your wounds pool. This is all well and good but it prompted a discussion on the nature of Hit Points.
As I've always described them to my new players; Hit Points represent your ability to avoid being hit as well as your ability to turn any serious hit into a glancing blows. It was a simple explanation and it worked but I never really questioned it until now. For the first part of that definition if hit points represent avoiding hits then why should armor apply. It certainly did in classic D&D when an attack that made it past your armor class (AC) reduced your hit points. Looking at it from that perspective armor merely served to turn away all inconsequential blows while an attack that would make it past your armor's defenses prompted a reaction out of you. Putting it into a narrative perspective this is represented by counting on your armor to absorb a blow but occasionally you will see an attack rapidly approaching a vulnerable point and it's up to you to duck under the beheading stroke. Examining the abstract nature of hit points again it stands to reason that reduction in hit points can be seen as fatigue setting in. It becomes harder and harder to parry, duck, dodge and weave until eventually the killing blow comes and that last hit point is mercilessly erased from your sheet.
Looking at it that way Armor could certainly be applied to hit points without the need for head scratching and lengthy explanations (except this one of course). Let's move a step beyond that and redefine hit points a bit. In the previous example Armor was the first line of defense turning attacks into a harmless clanging of steel on steel while hit points were a secondary defense occurring only when armor would be defeated. Let's switch things up a bit and reverse their roles. This time all attacks carry an air of lethality with them transforming hit points into your first line of defense while armor is the last barrier between you and death.
If this sounds familiar it's because I'm circling around an argument I made in my post about Defense regarding lines of defense. I haven't forgotten about defense and organizing these three into a hierarchy it goes something like this. At the top we have defense this serves the purpose of telling which attacks are considered a threat and which can be ignored and if you're feeling particularly bold laughed at. Below that we have hit points which represent your ability to get out of the way of a potentially life threatening attack. At the bottom we have armor which is there to stave off the attack that finally wears you down or in the worst case scenario the lucky critical that catches you off guard. Where things get interesting are the interactions between these three. Wearing heavier armor limits your Dodge defense which in turn means you are more likely to lose hit points and thus your armor will come into play faster and more often and vice versa. In essence heavy armor justifies it's own existence. Sounds silly doesn't it? Well in a game system where heavy and light armors should be viable these trade offs become a necessary evil intent on squashing the foolish dreams of your full plate fighter with an 18 Dex.
I have some more thoughts on redefining hit points, hit dice specifically, but I will save that for a later post.