THACO and its replacement
The THACO tables have always been a source of confusion, especially for me as DM. I don’t have multiple THACO tables set out in front of me for each monster and I the table lookup is simply much more work than it has to be.
THACO ,To Hit Armor Class 0, tells us the number you need to roll (equal or greater than) to hit a creature. A THACO of 15 means you need roll 15 or higher to hit someone with an armor class of 0.
Armor class is the most confusing part of THACO, because it’s very backwards. Unarmored is 10 and super crazy awesome armor is -10.
Here are a few examples:Everyone has THACO of 20 at level 1, so, without any other adjustments at level 1, to hit AC 0 you would need to roll a 20 or higher.
AC 5 is worse than AC 0, so at level 1, without any other adjustments, you would need to roll a 15 or higher to hit.
AC 10 is the worst armor class, so at level 1, without any other adjustments, you would need to roll a 10 or higher to hit. This is what I will convert from. 1-9 fail to hit and 10-20 hit. a 55% chance to hit at level 1
Our new system will start with the armor. It’s simple. Higher armor number means better armor. Every creature and character has a base armor class of 10 without any armor. So without any other adjustments, at level 1 you would need to roll a 10 or higher to hit an unarmored creature.
That undead lady with the magic missle wand would have been an armor class of 14, while Anuvier would have been 15.
That is the number ANYONE would have to roll or roll above to hit them.
Instead of changing your THACO table as you level, give your character a bonus to hit next to or above your, now defunct, thaco table. Each time your THACO would improve, just improve your to hit bonus instead. Whenever you roll to hit, just add your bonus and your roll.
Lastly, the defense adjustment that comes from your Dex score is going off of old armor class, so we need to switch that around too.