In recent weeks I have found myself, as part of an exciting new project I have embarked upon, doing a lot of synopsizing what some have come to see as complex or confusing concepts. One example that springs to mind is the old stat known as Armor or Armor Class (AC). In OD&D it was a really simple system that ranked plain old street clothes as AC9, while at the other end of the non-magical spectrum was plate mail and a shield at AC2
If Hit Points (HP) are considered to be your ability to avoid/evade a mortal blow (which they were in OD&D), then AC was how hard you were “to hit” (in this case threaten your well-being to some degree).
“To Hit” is another term that does not exactly mean what it seems to mean based on just the words. Confused yet? Consider “the Mountain” from Game of Thrones on HBO. This is one HUGE dude encased in metal. If three or four puny (normal-sized) guys attack him, chances are that their weapons will actually make physical contact with The Mountain lots of times; this is not what is referenced in “To Hit”. Of those several physical contacts, only a small proportion of them will actually strike with a potential to do actual damage; i.e. pierce the armor at a weak point or joint, or slice or pierce some flesh. Those are what are winnowed out of the combat to be represented by the To Hit number.
Back t0 AC; something as small and ephemeral as a pixie or sprite, or small and quick like a stirge would be somewhat difficult to simply swat out of the air like an over-sized wasp. To simulate that facet of their being I make them hard “to hit” by giving them a very good AC.
(OD&D had a descending AC system starting at 9 and going down; other systems use an ascending system, where 1 is street togs and 7 or 8 is really buff. Readjust this in your head to match your system; the concepts remain constant. Something slow and ponderous, such as a pachyderm, would be easier to strike, but the thickness of the skin somewhat mitigates this as well as the high number of HP an elephant or mammoth might have.)
AC does not always indicate what is being worn. AC is a combination of several concepts, not only the weight of the metal being worn.
To maintain perspective remember this: we were trying to bring miniatures to the table top. Several of the seemingly complex considerations and calculations were second nature to miniatures gamers. We tried to abstract a lot of what was second nature in minis to a whole new milieu—Table-top Role-playing (and this before it was even called role-playing).
Once this concept is grasped in the abstract, it then becomes more clear why extraordinary attributes can affect AC, or otherwise make the PC harder “To Hit”. These same attributes also can grant the PC more HP, all in recognition of how that last, fatal blow is just that, fatal. I have never counted anything more than “dead”; hit 0 HP and you died. Whether or not your PC can be Raised or Resurrected is another matter entirely. We had PC’s brought back from dead several times, although not always with absolute best results.
But anyway, that’s what we meant.