Monsters Never Miss

I had this idea a few years ago. I told it to James, and he didn’t like it. Maybe I didn’t explain it well, or maybe he just doesn’t like it. Maybe it’s a bad idea.

Let me know what you think! About the idea in general and about options I put forth in the “What I need to roll …?” question.

So what’s the big idea?

The idea is this: monsters never miss.

The title told me that much. What does that mean?

Normally in D&D style combat the player rolls dice to see if he hits the monster, then the Dungeon Master (DM) rolls dice to see if the monster hits the player’s character (PC). I’m proposing that the DM doesn’t make that second roll and we just assume that the monster is fearsome enough that it wouldn’t miss.

Wait! How is that fair?

You didn’t let me finish.

Instead of the Dungeon Master rolling to see if the monster hits, we let the player roll to see if the PC defends against the attack.

Mathematically it all works out the same, so everything is fair.

If everything is the same why bother?

I have a few reasons:

1. It keeps the spotlight on the PCs, instead of the monsters.

   This is the reason why I like “single roll” systems¹. The story is about the PCs, not about the monsters and the dice rolling should reflect that.

2. It keeps the rolls above board.

   If the player is rolling the dice, he knows that the DM isn’t fudging the results behind the screen.

3. It’s more heroic and pulpy.

   When you read a Conan story, Conan doesn’t emerge victorious because the enemy was bad at fighting. Conan wins because he was good at deflecting blows, dodging out of the way, and sometimes just getting lucky. But it’s always Conan’s fate that we care about, not the monsters.

What do I need to roll to defend?

I REALLY NEED SOME ADVICE ON THIS ONE

I’m torn between two methods: the static number method, and the look-up method.

What they have in common is that they’re both a 1d20 roll, of course. Because I vastly prefer “roll over” systems to “roll under” systems, so you need to roll a x or better.

Where they differ is the x.

Static Number Method

In the static number method you have to roll a 12 or over, but you have a penalty depending on how vicious the attacking monster is. So fighting a Night-Ogre (a 4 HD monster) would be a -4 penalty.

Advantages: Easy to remember, as “12” never changes.

Disadvantage: More math for every roll.

Look-Up Method

In the look-up method, the number you have to roll changes from monster to monster (so you have to look it up… get it?). The number would be part of the monster description, maybe call it “Offensive Class”² to match “Armor Class”? So when you look up Night-Ogre you see that it’s OC is 16.

Advantages: Less math on the fly. Defense works the same way as offense (look up the number and roll to meet or beat it)

Disadvantage: Every monster description now needs an OC added (though it’s easy to figure out). You need to look it up (though I guess you need to look up the AC anyway).

WHICH METHOD DO YOU THINK IS BETTER?

Are there any modifiers to the defense roll?

Of course! Any modifier that would have been part of your armor class is now a modifier to the defense roll. The normal ones:

Situation	Modifier
Dex 3	-3
Dex 4 – 5	-2
Dex 6 – 8	-1
Dex 13 – 15	+1
Dex 16 – 17	+2
Dex 18	+3
Shield	+1
Leather armor	+2
Chain mail armor	+4
Plate armor	+6

Also, any modifier that would have been applied to the monster’s attack roll is an “inverted” modifier (i.e. pluses become minuses and vice-versa).

If you’re using the Static Number Method the monster’s normal attack bonus is a penalty to your roll.

Example: Jalice has a Dexterity of 16 (+2) and is wearing leather armor (also +2), so she gets a +4 to her roll. She’s fighting a Night-Ogre when Brother Björn ³ casts a Daylight spell. Night-Ogres suffer a -2 penalty in daylight, so that means that Jalice gets another +2 bonus (for a total of +6) to her defense roll.

Look-Up Method: Jalice rolls 1d20+6 and needs to get a 16 or better to defend.

Static Number Method: Jalice gets another -4 to her roll (for the Night-Ogre’s attack bonus). +6 - 4 = +2, so she rolls 1d20+2 and needs to get a 12 or better to defend.

What about Player vs Player?

In a player vs player situation, players don’t get defense rolls but do get to use their armor class.

Why a 12 or better?

This part is about gaming math and probability. I saved it for last because I know that some people aren’t into that. If you’re one of those people, you can stop reading now. There’s nothing else in this post.

Let’s consider the simplest case. The attacker is a ½ HD kobold. The defender is a Brother Björn. He's a first level cleric with an average dexterity and no armor, resulting in an armor class of 9 in [o]D&D.

As you can see, the kobold needs to roll a 10 or better (on a d20) to score a hit. So 11 of the 20 possible rolls result in a hit. That means the kobold misses the other 9 times. As I said before, I really don’t like “roll-under” systems,⁴ so the 9 highest possible rolls are 12 – 20. So asking the player to roll a 12 or better to defend against the attack is mathematically identical to me trying to roll a 10 or better to hit them.

Let me show you the same information, but as a table:

Kobold’s Attack Roll	Result	Player’s Defense Roll
20	Kobold Hits	1
19	Kobold Hits	2
18	Kobold Hits	3
17	Kobold Hits	4
16	Kobold Hits	5
15	Kobold Hits	6
14	Kobold Hits	7
13	Kobold Hits	8
12	Kobold Hits	9
11	Kobold Hits	10
10	Kobold Hits	11
9	Kobold Misses	12
8	Kobold Misses	13
7	Kobold Misses	14
6	Kobold Misses	15
5	Kobold Misses	16
4	Kobold Misses	17
3	Kobold Misses	18
2	Kobold Misses	19
1	Kobold Misses	20

So that’s why a kobold would would have an Offensive Class of 12. As monsters get more hit dice, they’re more likely to hit. Rather than giving them a “plus” to hit, we achieve exactly the same result by giving the player a “minus” to defend. It all works out.

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Footnotes:

1. In a single roll system the player rolls an attack die. If he succeeds then he hits the monster, otherwise the monster hits him.↩

2. I really want to call it “Attack Class” but then there would be two “AC” stats.↩

3. Brother Björn, a cleric, was the first character I ever played. Way back in the late 1970’s, in Don Goulart’s basement in Rhode Island, I played my first game with Don, his brother Steve, and my good friend James. I didn’t have a character so they handed me this one. Later that night I went home and made my first character that was truly my own. That character’s name? “Snowgen,” of course.↩

4. It’s probably the 5 year old in me that thinks “more is better” for everything.↩