As I start my Don Quixote like quest for the perfect OSR system, I've come to realize that my quest doesn't start at the usual beginning. What I mean is, it doesn't start with classes, races, stats - because in the end, that is fairly inconsequential. The rules for the players isn't what needs to be simplified - most players love creating characters, tweaking stats, picking spells and the like. In truth, that can be bolted on from any OSR system if needed.
No, we need to take the engine that the players rarely if ever see and rebuild it with one thing in mind. Ease of use. We want to lighten the DM's load, so he can spend more of his time running the game session and less of his time running "the game".
So, the first thing I'm attacking is Monster Stat Blocks. Some of these can turn into a virtual run on sentence depending on the system. This is something I feel I need to simplify, as it it frequently referred to in game.
Without further ado, here's an my current idea for a OSR styled stat block. First I'll show it, then I'll explain it.
Ogre L 90’ (5) 17 / 1-10 / 4+1 {19} / Low / CE [4-190]
These 9’ tall lumbering humanoids are known to eat their victims raw.Alright, first we have the monster's type, in this case "Ogre".
The next two are "size" and "movement speed".
The bolded number in parenthesis is the Ogre's AC, followed by it's "base hit number" or THAC0.
Next section is the attacks it gets - in this case a single 1-10. If it got multiple attack, they would be separated by a comma.
Next up is "hit dice" followed by "average HP" (for the times you just down't want to roll - I was also thinking of given a low med / medium / high medium selection of numbers)
"Low" in this case refers to Intelligence.
CE is Chaotic Evil.
"4" is the Monster's Leve, and "190" is the XP value of the creature with average HP
The line of description is just that. It's a seed to get the DM in the right frame of mind for the creature, without the need for a full blown ecology and break down of it's society. Those parts are not needed in a game session, they are needed in game prep.
As an aside, I could just as easily turn the THAC0 into a +3 bonus in this case. Which I might do, as I think it might be cleaner.
Then, knowing PCs' AC (assuming AC -10 through AC10), you just add the bonus to PC's AC, take the total and add to the to hit roll. 20+ and it's a hit.