It's been a weird few months, with occasional crests of mental clarity and deep troughs of frustratingly impenetrable brain fog. For most of that time, my fantasy heartbreaker project, a.k.a. Goblins & Greatswords, has been relegated to a back-burner position and left to simmer. It turns out that back-burner simmering is good for gaining new perspective on things. This is mostly a thinking-out-loud sort of post; nothing's set in stone. Any comments or insights from other minds are welcomed and encouraged.
First off, I'm thinking of shooting one of the most sacred cows of D&D-like RPGs: The d20 combat attack roll. Instead, I'm looking at a roll of 1d12 plus an exploding weapon die. (Whenever the maximum is rolled on the weapon die, roll again and add to the total.) Weapons that are difficult to use or have weak armor-penetrating ability get a smaller weapon die, like a d4, while those that are easy to use and/or good at breaking through armor get larger dice, i.e. d6 or d8. Damage would still be capped depending on the weapon type. As before, the objective is to beat the target's AC (ascending), with one point of damage scored per point the roll exceeds the AC, up to the cap.
The most basic system would be to simply assign d4, d6, and d8 weapon dice to light, medium, and heavy weapons, which would have damage caps of 4, 6, and 8 points respectively. An advanced option might assign weapon dice and damage to each specific weapon type. Thus, you could have weapons that are relatively easy for an untrained combatant to use but less damaging, and weapons that require more skill to handle but potentially deal bigger damage. Maybe a war hammer uses a d8 weapon die, with max damage of 4, while a sword uses a d4 and max damage 8. A good all-around weapon might be d6/6.
Monsters would probably just use d6, with their Hit Dice accounting for most of their combat ability.
This is, in principle, quite similar to simply adding flat bonuses or penalties to attack rolls, but using an extra die instead injects a little more randomness. It's also, I think, easier to remember than a + or - modifier to a roll, because it's an integral part of the roll, not something tacked on as an afterthought -- though maybe that's just me. And hey, finally the d12 gets some serious love. We're talking one of the game's most often used mechanics.
It also introduces some potentially useful and interesting quirks. For one, characters attacking unarmed obviously wouldn't roll a weapon die with the d12, so unless they're highly skilled fighter-types, they probably won't have much success punching a guy in plate armor (AC 16.) That seems like a good thing to me. It also means that grappling a weapon-user is more difficult, even if the opponent is completely unarmored, since achieving a grapple requires beating the opponent's combat roll, not its AC.
Also, with two dice in play, there are at least four different "critical" conditions. Rolling 1s on both the d12 and weapon die makes for a critical fumble of some sort, typically resulting in loss of the next combat action. A 1 on the d12 and max on the weapon die might mean the weapon breaks. A 12 on the d12 is a critical hit -- damage is uncapped! If the weapon die explodes on the same roll, the target could be in a world of trouble.
Outside of combat, I'm rethinking how thief-like skills could be handled. A binary pass/fail roll isn't usually very exciting, and there's not much player agency involved. Could thief skills be reworked to be more exciting and engaging? Maybe.
Let's scrap the percentages, and instead express skills as a simple bonus, ranging from +1 at 1st level up to somewhere around +12 to +16 for level 15. Expressing it as a bonus implies that the character is just better at things that anyone can attempt -- starting off only slightly better, but eventually completely outclassing the untrained. That's a pretty good parallel for combat, which the rules allow anyone to do, but fighters are just better at it.
Want to pick a lock? Any fool can try, but a character with some skill at Tinkering has the best chance. Roll a d6 and add Tinker bonus, if any. What do you need to roll? Depends on how good the lock is. A cheap lock takes a 5, a good one a 10, and a masterful one a 15 or even 20. Didn't make it on the first roll? Keep trying, if you've got time to burn! Each attempt takes a full turn, but the rolls add up. Just don't roll a 1 -- that wipes out all your previous progress, and if you do it twice in a row, you're just stumped and can't figure out that lock. Think you're a lock-picking ace? Get twice the difficulty level of the lock in a single attempt, and you crack it in just one round!
Same thing goes for disarming a trap. If you get two 1s in a row, you accidentally set it off.
How about stealth? A binary result -- either you're detected or you're not -- is lame. Instead, if there's someone who could potentially notice you, the GM rolls 2d6 and subtracts your Stealth skill bonus. Multiply by 5, and that's how close you can get before you'll be noticed. If the result is zero or negative, you can sneak right up under their noses! Oh, but the GM won't tell you the number. You'll never know for sure just how close you can get until you actually try. Sneaking past a monster at a fair distance is relatively safe and simple. Skulking right up behind it to take its key ring is lot more daring.
Hear noise (or, more generally, Alertness)? The GM rolls 2d6 for you and adds your bonus, making it harder for someone to sneak up on you. If the other guy has Stealth, his bonus is subtracted; the two abilities work against each other. Listening down a corridor or through a door? Roll 2d6, add your bonus, multiply by 5 if through a door or 10 otherwise, and that's how far away you can discern something at the volume of typical speech.
I haven't yet sorted out how to bring every thief skill into this model, but I'm liking it so far.