Everyone Has 10 HP

 I think it would be fun to make a ruleset where everyone has 10 HP--dragons, PCs, everyone.

Nothing invigorates a return to blogging like slapping a few sacred cows.

Variant 1: Everyone Has 10 HP

Maybe we can have the actual range be 8-12 HP for the spectrum of unarmored wizards to armored fighters, but let's just assume 10 HP for now.

The trick that makes all of this work is that things deal more or less damage based on what level they are.

If you are attacking someone the same level as you, you'll deal 1d6 damage on a hit.

If you're higher level, you'll deal more damage.

If you're lower level, you'll deal less.

If your target is:

8 or More Levels Higher Than You: 1 damage

6 or 7 Levels: 1d2 damage

4 or 5 Levels: 1d3 damage

2 or 3 Levels: 1d4 damage

0 or 1 Levels Higher: 1d6 damage

1 or 2 Levels Lower: 1d8 damage

3 or 4 Levels Lower: 1d10 damage

5 or 6 Levels Lower: 1d12 damage

7 or More Levels Lower: 1d20 damage

This is bidirectional, so if you're fighting an enemy that is 3 levels higher than you, it'll deal 1d10 damage to you, while you'll only deal 1d4 damage to it.

A bunch of level 1 mooks attacking a dragon would only deal 1 damage per attack.

A dragon attacking them would deal 1d20 damage per attack.

The same dragon, attacking a level 4 knight, would only deal 1d12 damage, which the knight has a good chance of surviving.

Discussion

I picked 10 HP and 1d6 damage as the midpoint because then the average character takes ~3 hits to die.  If you assume that only 50% of attacks deal damage, then that is an average of 6 attacks from an equal-level foe.  If that seems too high or too low, you can easily adjust the baseline of 10 HP.

This also risks making low level enemies too durable (who wants to take 3 hits to kill a goblin?), so if you want your low-level enemies to die quicker, you could always rule that Level 3 enemies have 8 HP, Level 2 enemies have 6, Level 1 enemies have 4, and Level 0 enemies (like goblins) have 1 HP.  A statblock would look like: 

Goblin: Lvl 0, HP 1, Def leather

The advantages is that the world will always be scaled for you.  A fall that deals 1d6 damage will be equally threatening no matter what level you are.  Healing potions will always be scaled, and so on.  If you deal 6 damage to something, you know that it's lost most of its health.

There are plenty of disadvantages, though.  It's probably counterintuitive, in a few ways.  Players don't get the satisfaction of watching their HP go up every level.  Spells don't have an obvious way to scale (although if you wanted to keep using the GLOG dice, you could say that the spells function like an attack with a Level equal to character level + 3 for every MD invested beyond the first).

Variant 1.1: Replacing the d20 Roll with a Coin Flip

It's pretty easy to run a tabletop RPG using only a coinflip like I describe here.  (I've actually had the opportunity to playtest this since writing it.  If I could rewrite that blog post I would make it simpler.)

Marcia also collected some similar ideas here.

But, since we're simplifying the whole spectrum, we might as well strip out the d20 attack roll, too.

Armor gets abstracted into HP, with higher armored foes getting +1 or +2 HP.  

Attack bonuses are already baked into the Level vs Level consideration above.

If we want to keep fighters better at fighting, then we could always say that fighters fight as if they were 1 level higher, and get +2 HP relative to the wizard.  Alternatively, you could just give fighters 1-2 active abilities, which addresses that category of player who thinks that fighters are boring and have fewer combat options.

So a statblock now looks like: Owlbear, Level 5, HP 10

I've always despised fiddly +1 modifiers/improvements to d20 rolls, but one I thing I like about coinflips is that these little bonuses are impossible under such a system.  Good triumphs when evil has no place to take root.

(If you want to use a coin flip for things like skill checks, please see here.  As usual, Chris says it better than me.)

Variant 1.2: Removing Damage Rolls

Our little game engine is getting pretty fast, but we could make it even faster if we could remove all those stupid damage rolls.  There's some math involved here, but a good trade-off between simplicity and consistency is probably this:

Naked wizards have 15 HP.  Armored warriors have 21 HP.  The average PC has 18 HP.  

Enemies have 18 HP (or if you want to randomize, 2d6+10 HP or something similar).

Against a foe of the same level, you deal 6 damage if your coin flip comes up heads.  For every level lower, you deal -1 damage, down to a minimum of 1.  For every level higher, you deal +2 damage.

So level 1 PC attacking a level 2 orc will do 5 damager per hit.  The same orc will deal 8 damage per hit. 

A level 1 PC attacking a dragon will deal 1 damage per hit.  The dragon will deal a whopping 24 damage with a single hit.

If you would normally get bonuses/penalties to attack rolls/damage, this instead translates to increases in the effective level.

You might think that this would make combat predictable, but (1) if you are using randomized HP, enemies will still take an unknown number of hits, (2) players will have different levels and will deal different amounts of damage, and (3) situational bonuses/penalties add another layer of noise.

If you want to use GLOG magic, then just say that [sum] = effective level, and calculate damage that way.

I love AI-generated art.
I've been saying for years art needs more fingers per hand, but only the computers listened.

Variant 2: Removing HP

Holy shit, Break!! is looking good.  It makes me want to make a game with no HP, just hearts.

Since the average PC can survive three hits from an equally leveled foe, why not just give them 3 hearts and be done with it?  It's very similar to "everyone has 10 HP" except less granular and much cuter.

We probably can't use coin-flips anymore (since that removes too much granularity from the game) so we'll have to go back to d20 rolls.

In this version, you have an attack bonus equal to your level.  Whenever you make an attack, you roll d20+[attack bonus] and need to equal-or-exceed 11+[enemy level].  Fighters can have a bonus to both their attacks and their defense.  Critical hits and fumbles exist.  Environmental hazards like poison gas and falls need to have levels assigned to them.

This shares the same problem as above, where goblins take too many hits to kill, so perhaps monsters have hearts equal to their level.  This keeps it closer to D&D--but you could also create a maximum number of hearts (e.g. 6 hearts) and find other ways to differentiate your high-level dragons and liches.

Up to you if you want this to apply to PCs or not.  "A Level 1 PC should die in 1 hit" is very fun and old-school, but I've been slowly moving towards "A Level 1 PC should die in 2 hits" and that is also a cool and valid school of thought.

A valid criticism of this is that it is essentially the opposite of bounded accuracy.  A low level party attacking a dragon is going to be missing a lot, and when everyone spends their turn without any progress towards their goal (enemy HP decreasing), it feels bad.  So you may want to limit effective enemy level and simply give your high level monsters more hearts and additional attacks instead.  It might still take the same average* number of attack rolls to kill the lich, but it feels better.

*the variability is also lower this way, too.

There's some risk of dissonance if a level 10 dragon can't kill a level 1 adventurer in a single round, but if the dragon has 3 attacks, it can still shred someone fairly quickly.

Discussion

All of these are cool, but they change the basic math of D&D.  They are no longer perfectly compatible with published adventures.  (One of my goals with the GLOG was the ability to pick up an old published B/X module and be able to run it on the fly.)

They are all mostly compatible when dealing with similarly-leveled foes, but will scale differently against higher- and lower-level ones.  As a DM, this means that you can no longer rely on your instincts that say "yeah, I can put 20 goblins in this room for a level 3 party".

Another big difference is that these methods effectively scale your damage with your level, which is something that doesn't really happen in normal D&D.  Your HP scales as you level, but your sword doesn't deal more damage.  (I mean, it does in 5e, because your abilities do, but not in most OSR games.)  So if you use the stuff on this page, be aware that fighters are more powerful at higher levels than you would normally expect.

Most of them are faster than regular OSR play, although it may get tedious looking up weapon damage every time you attack a new PC (in method 1.0).

Out of everything above, I'm probably most interested in 1.2, which dodges the damage-lookup I complained about in the previous paragraph and looks like it might be worth a playtest.