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I love hit points. They’re a brilliant abstraction, though often misunderstood, and they work beautifully in play.

I double-super-love that in OD&D, how you roll them for your character is completely open to interpretation. I don’t think that’s been true since the late 1970s, as each edition since has spelled things out much more clearly.

This isn’t news, and I’m not a scholar uncovering D&D’s Hidden TruthsTM. These two threads on the Original D&D Discussion boards are both great reads on this topic: In defense of the original HD system and Origins of hit point re-roll at every new level?. I’m just a dude exploring old-school D&D and having fun poking things with a stick, and one of my maxims is that everything is new to someone.

It’s fun to talk about this stuff, and here on Yore is where I like to talk about it.

OD&D: Dice for Accumulative Hits

Here’s OD&D on rolling hit points:

Dice for Accumulative Hits (Hit Dice): This indicates the number of dice which are rolled in order to determine how many hit points a character can take. Pluses are merely the number of pips to add to the total of all dice rolled not to each die. Thus a Superhero gets 8 dice + 2; they are rolled and score 1, 2, 2, 3, 3, 4, 5, 6/totals 26 + 2 = 28, 28 being the number of points of damage the character could sustain before death.

That first sentence seems clear enough: you roll hit dice to find your hit points. And the second sentence just explains what “3 + 1” means: add the “+ 1” just once, at the end. So far, so good.

Then we get to the example. “Superhero” is the title for an 8th-level fighting man, listed as “Super Hero” in the chart. At 8th level, our doughty fighting man gets 8 + 2 Dice for Accumulative Hits — and in the example, they’re all rolled at once.

I don’t think I’d have noticed this on my own. If I hadn’t stumbled across folks talking about hit dice online, and then read those two threads above, I’d almost certainly have assumed you rolled HP the same way in OD&D as in every other edition — and maybe you do! Which is the neat part.

Consider this: Which of these is correct?

  • The fighting man adds 1d6+2 to his existing hit point total (which has been going up by 1d6, sometimes with a small bonus, every level).
  • The fighting man rolls 8d6+2, and now has that many hit points. It doesn’t matter how many he had before — this is a fresh roll.

I don’t see anything in OD&D that clarifies this, which suits the game’s DIY spirit just fine in my book. But if that second option, rerolling HP every level, sounds weird, consider Empire of the Petal Throne.

EPT: Hit Dice

M.A.R. Barker’s Empire of the Petal Throne came out in 1975, just one year after OD&D, and it does a lot of things exactly the same way as OD&D — but not everything. That makes it an interesting counterpoint to D&D in some respects, notably this one.

As each player enters the game, he or she shakes on 6-sided die to determine his or her available hit dice points. As each succeeding level of experience is reached, the indicated number of 6-sided dice are shaken to determine his new total.

And, later in that same section:

No character may ever have LESS hit points at a higher level than he did at a lower one. This, if a warrior shook two 5’s and had 10 hit points at level II, and then on reaching level III shook three dice but got only a total of 7, he adds 3 points to maintain his total at his previous 10. He must always equal his previous total, although he may not be lucky enough to surpass it.

Much clearer than OD&D: You roll hit points anew each level, keeping the new total if it’s higher.

Which is pretty wild! I’ve never played D&D that way, and it sounds like it’d be fun to try.

But what did Gary and Dave actually do?

As far as I can tell, whatever they thought best. Here’s Michael Mornard, one of the original playtesters of OD&D, on the subject:

Gary used to give us the option of rolling an additional die, or rerolling all your hit dice. However, if you rerolled them all, you took the new number, period.

You could also reroll at the beginning of an adventure, rerolling them all.

c. 1972

Not sure how Dave did it.

So at Gary’s table (at least during that time), you not only got to choose which option to use — from the two we’ve already looked at, additive rolling or full reroll — you could also reroll at the start of an adventure. And either way, there’s none of EPT’s “keep the highest.” Nifty.

Update (March 11, 2016): By way of an excellent post on Necropraxis, Rerolling Hit Dice & Healing, I found a direct quote from Gary on EN World on the topic of hit dice:

Everyone I know of kept hit points as rolled.

Gary also notes that the omission of a spot to record HP on the OD&D character sheet was an oversight, so it seems likely that he was doing this — roll and keep — in that same general time period.

Drop some math

My gut sense is that rerolling HP every level would make all PCs’ HP trend towards the mean — average out, basically. No one gets hosed by one or two bad rolls (at least not for long), and no one enjoys wild advantages based on very lucky rolls (ditto). But I can’t back that up with math.

Fortunately, Compromise and Conceit has the stats background to delve into the differences between these two methods. Here’s one of the bits I understand, a handy takeaway:

This does not have a central distribution: it reduces the probability of getting small numbers rapidly, and drives the weight of the probability distribution towards the maximum.

Fascinating! My gut is apparently totally off.

I love the fuzziness of OD&D in areas like this. It’s a feature, not a bug, and it encourages individual groups to develop their own approaches to the game. Just as Gary and Dave almost certainly weren’t playing the same game even as they were publishing it[1], playing OD&D looks like it requires a willingness to make up all sorts of things on the fly — including how you handle something as central as characters’ hit point totals.

And just like every time I’ve delved into OD&D, this makes me want to run it more than ever.

[1] This is just one of so many things Jon Peterson‘s stellar Playing at the World has been illuminating for me. I suspect I’ll be blogging about PatW at some point — it’s so good!

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