by Ramanan Sivaranjan on December 23, 2014
I have been using ascending AC for my OD&D Carcosa game. Players roll a d20 to hit, add their attack bonus, and try and score higher than their opponent’s AC. An unarmoured combatant has an ascending AC of 10; plate armour and a shield confers an AC of 17. It’s a much simpler system for adjudicating combat in my opinion. People know if they have hit or not without having to look at a table, and the arithmetic is all quite straight forward.
What follows are the tables from the first OD&D book MEN & MAGIC redone so they work with ascending AC. (I am certain I am not the first person to do this, but there wasn’t an obvious hit when I looked on Google.)
The attack bonus progression for the Fighters is:
And for Magic-Users:
Monsters use the following table.
|up to 1||+0|
|up to 2||+1|
|up to 3||+2|
|up to 4||+4|
|up to 6||+5|
|up to 8||+6|
|up to 10||+8|
The tables are simple enough to make. In a descending AC system a first level characters needs to roll a 10 to hit AC 9 (an unarmoured person), which we determine by looking at the attack table in MEN & MAGIC. To hit that same character who has an ascending AC of 10 by rolling a 10 (or more) implies a 1st level character has no attack bonus. A 4th level fighter only needs an 8 to hit that same character, so their attack bonus is +2.