If you want to release a B/X (or OSE) compatible retroclone, you’re welcome to use E9. It’s got most of the same streamlining as Shadowdark, handles combat and exploration a little more tactically, and runs remarkably fast.
You can download it from itch.io here.
The engine is slightly cleaner than the one published with Materia Mundi; combat’s a little faster, there’s a little bit less fiddly stuff to track, and so on. But it’s the exact same engine - think of E9 as a small set of errata; if you use one or the other, you won’t notice any changes 99% of the time.
I’ve gone through the design philosophy and details several times while discussing Materia Mundi, but it never hurts to go through them again. So:
E9 Core Mechanics
E9 only uses two dice: the d20 and the d6. The d20 is used for attack throws and saving throws; the d6 is used for literally everything else.
Difficulty
The core resolution loop of E9 is simple:
The referee describes the situation
The player tells the referee what they want to do about the situation, describing in detail what their character is actually doing
The referee decides on one of five difficulties, based on their intuitive understanding of the situation and the action the player is taking:
Automatic (don’t bother rolling; you accomplish your goal)
Easy (roll 2 dice; if either beat your threshold, you accomplish your goal)
Normal (roll a die; if it beats your threshold, you accomplish your goal)
Hard (roll 2 dice; if both beat your threshold, you accomplish your goal)
Impossible (don’t bother rolling; you can’t accomplish your goal that way)
Play continues
That’s it; it’s really that simple. All the rest of the rules are just specifying what die to roll, what threshold to roll it against, and when to adjust the odds in either direction.
The Formula
All attack throws and saving throws are determined using the same simple formula. Player characters, NPCs, and monsters all follow this formula; it’s basically the “core engine” of the game:
Level + Ability: -2 -1 0 1 2 3 4 5 6 7 8 9 10+
Threshold: 17+ 16+ 15+ 14+ 13+ 12+ 11+ 10+ 9+ 8+ 7+ 6+ 5+
That’s it. Add your level + ability, and subtract them from 15 (to a minimum of 5+); every creature in the game follows this exact progression. (Monsters use hit dice instead of level, but they’re the exact same number). Each ability governs a different saving throw:
Constitution determines your save vs. Doom (poison, death, that sort of thing)
Strength determines your save vs. Hold (paralysis, petrification, being knocked down); it also determines your Melee attack throw.
Dexterity determines your save vs. Blast (dragon’s breath, fireballs, lightning bolts, etc); it also determines your Ranged attack throw.
Intelligence determines your save vs. Trick (Illusions, mind control, and so on)
Wisdom determines your save vs. Curse (all detrimental spell effects not otherwise specified)
Charisma determines your save vs. Fear (morale checks, emotion-manipulating spell effects, and the like)
Talents
Anything that isn’t combat-related is handled by a talent instead. Talents are “n-in-6” rolls, following the excellent system presented in games like Dolmenwood or Lamentations of the Flame Princess. E9 takes this a step further, and codifies 12 talents, linking them to 4 of your 6 abilities:
Dexterity
Agility is your climbing, tumbling, and acrobatics skill.
Finesse is your crafting, lock-picking, trap-disabling, and pick-pocketing skill.
Stealth is your hiding, sneaking, and moving silently skill.
Intelligence
Lore is your academic knowledge skill, as well as knowledge of “folk wisdom”, religion, and the supernatural.
Medicine is your knowledge of how to treat injuries, poisons, and diseases.
Science is your engineering and “natural philosophy” knowledge skill, which includes the understood rules of magic and occult phenomena.
Wisdom
Alertness is your ability to spot ambushes, traps, secret doors, and the like.
Intuition is your “gut sense” of danger, people’s motives, and so on.
Survival is your practical knowledge of nature and how to navigate, hunt, forage, find shelter, and otherwise survive off the land.
Charisma
Bearing is your ability to project confidence and leadership, and to inspire or intimidate others.
Charm is your ability to influence other creatures’ regard for you.
Wit is your ability to convince other creatures to believe you about facts, or to convince them to pursue a particular course of action.
For each of these talents, your abilities determine their starting values:
If your ability is -3, all three linked talents start at 6+
If your ability is -2, two linked talents start at 6+ and one starts at 5+
If your ability is -1, two linked talents start at 5+ and one starts at 6+
If your ability is +0, all three linked talents start at 5+
If your ability is +1, two linked talents start at 5+ and one starts at 4+
If your ability is +2, two linked talents start at 4+ and one starts at 5+
If your ability is +3, all three linked talents start at 4+
This means that most characters have a 33% chance of pulling off most skilled exploration actions, but good or bad abilities can adjust this to 17% or 50%.
Classes
E9 groups classes into 3 fundamental “roles”: Fighters, Experts, and Magic-Users. All classes that share a given role operate functionally the same.
Fighters
Fighter classes get the cool combat perks. They can perform the guard action, which lets them interrupt other creatures within reach of their weapon by attacking them. They also get improved critical hits, inflicting a critical hit whenever they beat their own attack throw threshold by 10 or more. At levels 2, 4, 6, and 8, they get to pick a fighter feat and expand their options during a fight.
Experts
Expert classes get to improve their skills at each level, choosing which skill to improve each time. This improves that skill’s base chances by 17%, up to a maximum success rate of 83% at normal tasks. Different expert classes will have different skills that are their “default expertise”; actions that they take with those skills will be easier than the same actions taken by those without expertise.
Magic-Users
Magic-User classes get access to the magic system, gaining a Vancian “pool” of magical effects that they can prepare and then cast. Each magic-user also gets two skills that improve at a regular schedule, but slower than an Expert’s (one skill improves at levels 2 and 6; the other improves at levels 4 and 8). One of their two skills can also be used to attempt to re-prepare their magical effects within the dungeon, if they are willing to risk being vulnerable for the time it takes to do so.
Compatability
E9 is probably 90% to 95% compatible with OSE, Dolmenwood, Lamentations of the Flame Princess, Shadowdark, and so on. It’s pretty easy to “drop in and go”, since they’re all built on the same underlying B/X core.
I just think you’ll have more fun using E9’s version of that core.
