Charles McEachern posted on his site some ideas for reworking D&D. The roll-under idea reminds me a lot of Searchers of the Unknown, so I wanted to see what all the ideas in one place would look like.
To make this easy, we'll start with my favorite D&D in miniature ruleset, Microlite 20 Legacy. If it looks like it works well, maybe we'll expand it out to my ruleset of choice, Swords & Wizardry.
There are 3 stats : Strength (STR), Dexterity (DEX), and Mind (MIND). Roll 3d6 for all stats.
Per the original article, there are no stat bonuses. That means that rolling 4 dice and dropping the lowest makes feels too powerful. More on that in a moment.
There are just 4 skills : Physical, Subterfuge, Knowledge and Communication. For each skill, a player has ranks of advantage, disadvantage, or zero. Advantage allows the player to roll extra dice in their attempt to succeed at a task. Having advantage means you roll a number of extra dice and use the lowest result. Disadvantage also allows the player to roll extra dice, but this time the highest result is used. If a character has a skill of zero, no additional dice are rolled, the result of the lone die stands. There is a maximum of 5 dice of advantage.
For example, if a character's Skills are Physical 2A, Subterfuge 0, Knowledge 1D, Communication 1A. Any task that is Physical allows the player to roll two extra dice and have advantage. The lowest result of the three dice is used. However, any task that tests a character's Knowledge adds one extra dice to the roll, but the highest result is used. Any task that require Subterfuge adds no extra dice to the roll.
The GM chooses which stat applies to the character's chosen task. Climbing, for example, would provide extra dice per the Physical skill and require the player to successfully roll-under the STR stat. Finding Traps would use the Subterfuge skill to determine advantage or disadvantage and require a successful roll-under the MIND stat.
Since everything is resolved by roll-under stat, skills work differently. I thought about having a +1 represent an advantage of 1 extra die and -1 a disadvantage of one extra die, but that seems confusing to have -1 use the highest result of two dice. So, I made it 1A and 1D.
Note that there are no “saving throws” in this game; use the Physical skill rolling under STR for Fortitude saves and the Physical skill rolling under DEX for a Reflex saves. Saving against magic depends on the spell. The Communication skill rolls under the MIND stat for Charm or Enchanting type of spells. (This is the closest thing to a Will save.) The Physical skill rolls under the MIND stat for any kind of attack spell. The Subterfuge skill rolls under the MIND stat for any kind of detection spell. The Communication skill rolls under the MIND stat for any kind of Divination spell, including spells like ESP.
Saving Throws change the most from M20 because level cannot be used. The interesting thing, though, is that there is variation to the types of spells that affect characters more than others. More on that later.
The classes are Fighter, Rogue, Mage, and Cleric. Characters begin at Level 1.
Fighters wear any kind of armor and use shields. They start play with 1 die of advantage in the Physical skill.
Rogues can use light armor. They start play with 1 die of advantage in the Subterfuge skill.
Rogues have a special ability to perform a sneak attack. By using their Subterfuge skill to roll under their DEX stat, they have a chance to do extra damage. Their Subterfuge skill rank determines the number of extra dice used for an advantage to roll for damage.
Magi wear no armor. They can cast arcane spells, and they start play with 1 die of advantage in the Knowledge skill.
Clerics can wear light or medium armor. They cast divine spells. They start play with 1 die of advantage in the Communication skill.
Clerics have a special ability to Turn Undead. By using their Communication skill to roll under their Mind stat, they can make undead creatures run away and possibly destroy them on the spot. Their Subterfuge skill rank determines the number of extra dice used for an advantage with twelve-sided dice. If the result is greater than the undead creature's hit points, it is destroyed. This is counted for each undead within range. If the result is less than their current hit points, the undead creature will take damage if it does not flee. A Cleric can use this ability a number of times a day equal to their level.
This gets tricky with Turning Undead. Normally the DC is the undead's hit points, but that doesn't work in this system. Using the workaround posted above, hit points will need to be lower for creatures overall. This could work well. After all, dragons in Dungeon World only have 16 hit points. It's all in Damage Reduction...
I was really happy with how the Sneak Attack worked. Thinking about how the Rogue uses Advantage to determine damage makes me think of how to change magic items. After all, without bonuses or penalties to rolls, there are no +1 swords, right? However, there can be 1A swords and 2A swords. There can even by 1D cursed swords.
Humans choose one level of advantage to one skill.
Elves get +1 to their MIND stat
Dwarves get +1 to their STR stat
Halflings get +1 to their DEX stat
Since advantages stack, humans can get a real head start at 1st level.
Magi can cast any arcane spell, and Clerics any divine spell, with a spell level equal or below 1/2 their class level, rounded up. They have access to all arcane or divine spells in the spell list.
When Magi cast a spell, they use the Knowledge skill to roll under their MIND stat. Clerics use their Communication skill to roll under their MIND stat.
Successfully casting a spell of any kind costs a number of hit points equal to the level of the spell being cast.
How's that for a subtle change? Missing the roll on casting a spell costs nothing, successful spellcasting costs hit points. I did this because hit points are lower throughout the entire game. It may be worth generating a Mana Point system, but I'll look at that another time.
Now for Combat:
Hit Points =STR Stat. If HP reach 0, unconscious and near death. Further damage directly reduces STR. If that reaches 0, death.
Roll one d20 using the Physical stat for advantage or disadvantage. Initiative order is determined by lowest roll to highest. Everyone can do one thing each turn; move, attack, cast a spell, etc.
Melee attacks = Physical skill roll under STR stat
Missile attacks = Physical skill roll under DEX stat
Magic attacks = Knowledge skill roll under MIND stat for Magi, Communication skill roll under MIND stat for Clerics.
A successful combat roll does damage. Each weapon or spell has a die to roll for damage. The referee rolls the opponent's armor rating and the result is subtracted from the damage. Damage cannot be reduced to less than zero.
Fighters and Rogues can roll under the DEX stat if wielding a light weapon. Fighters and Rogues can wield 2 light weapons and attack with both in a round if they take 1 level of disadvantage on all attack rolls that round.
If the total advantage on a melee or missile attack is 3 or more ranks a second attack can be made with 2 dice disadvantage applied. If the total advantage is 5 ranks, a third attack can be made with a 4 dice disadvantage.
For example, if the total bonus is 5 ranks of advantage, three attacks can be made. The first has 5 ranks of advantage, the second has 3 ranks of advantage and the third has 1 rank of advantage.
Whew! Now advancement.
Challenge Level is specific to the defeated monsters or the given CL for the trap, situation, etc. Add +1 to the CL for each doubling of the number of foes. For example, 1 kobold is CL 1, 2 kobolds is CL 2, 4 kobolds is CL3.
Add up the Challenge Levels of every encounter. When the total = 10* your current level, you've advanced to the next level. Reset the total to 0 after advancing.
Each level adds only one of the following:
+1d6 Hit Points
1 Rank of advantage
+1 to a stat
Clerics and Magi gain access to new spell levels at levels 3,5,7,9,etc.
Example: The 1st level adventurers have just completed a dungeon adventure, and defeated CL1 creatures, a CL2 trap and the CL3 leader. That's a total of 10 Challenge Levels, so they all advance to level 2. They need to defeat another 20 Challenge Levels to reach Level 3.
This gets hairy in places, but it still works. The PDF with Monsters on the next post.