I adapted it from another old school fantasy rpg and converted it to AD&D.
Hit points and THAC0 are no longer in use; instead of them, we will use PR (Physical rating) which incorporates both. You will see how later in the rules.
FIRST STEP: You always roll 4D6 for each of your ability, and discard the lowest roll.
After finishing rolling for your abilities, take your scores in Strenght and Constitution and make the sum of them. Also, add your Constitution bonus. What you get in the end is your PR (Physical rating) score that it is of paramount importance during combat.
SECOND STEP: Calculate your DR (Defense rating). It depends from the kind of armor you use plus your dexterity bonus. If you use the shield, you add one point to your DR. keep in mind that under this system the "armor class" is ascending.
THIRD (and final) STEP: Now we get to the combat phase. Suppose you are fighting a skeleton.
The attacker rolls 2D10 (1D10 for TENS and 1D10 for ONES).
The skeleton has PR 10 and DR 2 and fight with short sword (1D6 damage).
Suppose I (the fighter against the skeleton) have PR 25 and DR 4 (leather plus shield).
I now roll 2D10. Looking on the combat matrix, i have a 90% chance of hitting the skeleton. I score a 96% (how unlucky!), missing.
Now the skeleton. From the combat matrix, i learn that it has 55% chance of hitting me.
It rolls a 43, so i got hit. It rolls 1D6 for damage, getting a 5. I got 5 points of damage that i have to deduct from my PR. I am more fatigued and wounded now, so on my next roll i will cross index on the combat matrix using my actual PR of 20 (25-5).
So on the next round my chance of hitting the skeleton instead of being 90%, has dropped to 85%
Should a creature's PR= -10, then the creature is dead.
In the next post i will cover two other topics, namely: How to recover your lost PR, and PR advancement.
