Wednesday, July 29, 2020

Plan It By the Numbers - Frank Mentzer & setting encounters in D&D

In Gary Gygax's article "FIRST ADVENTURES IN DUNGEONEERING (by Gary Gygax, USA)," discussed here yesterday, I made this comment in the comments section:

"It's true, but the core idea for me is that you have a chance - to win by fighting, to win by outwitting, to evade by running. Since your options on all three are really level dependent, ultimately, it's really saying that balanced decisions about appropriate encounters are part of the basic job of the GM. It's not a numeric system like you'd find later for BECMI D&D, but it's still help up as a basic element of dungeon design. It's still on the continuum of balancing risk and reward and capabilities of the PCs that ends in scaled encountered."

Wait, what? BECMI had a system for balancing encounters?


Dragon #101 had an article by Frank Mentzer, author of the Basic, Expert, Companion, Master and Immortals D&D rules - the BECMI system.

Plan it by the numbers
A system for tailoring challenges to characters
by Frank Mentzer

It includes this:

"Author’s note: The following was in-
cluded in the original manuscript for the
D&D® Master Set. It was, however,
thought by the editors to be too heavily
mathematic for easy use, and was replaced
by an alternate system. But I still like this
one, and use it in my own campaign —
though modified for AD&D® game use.)"

What followed is a mathematical system for balancing encounters for PCs.

The system took the Average Party Level and Total Party level into account, along with a % of that - from up to 20% of TPL (for an easy wandering encounter) to over 200% of TPL (extreme danger, run or die). You could/should also compare to the Average Party Level, with the same relative strength (from nuisance encounter - amusingly, the same term I use for such in my own games - to "extremely dangerous opponent."

You'd use the HD, HP, us a multiple based on the "Power Index" (number of *s next to their HD) to determine a numerical value, compare, and go from there.

Take these examples (column width not adjusted - this is just cut-and-paste):

"A. Low Level Party; size = 5, TPL 26,
APL 5.2
Situation #1: Wandering encounter
1. Impact desired: Average opponent,
average encounter.
2. HD of one monster: 90-1 10% APL, or
90% of 5.2 to 110% of 5.2, or 4.7 to
5.7. Average = 5.2; monster chosen:
cockatrice (HD 5**).
3. Power Factor: 2 (asterisks).
4. Total monster HD: 30-50% TPL, or
30% of 26 to 50% of 26, or 7.8 to 13.
5. Number appearing: 7.8/5 to 13/5, or
1.56 to 2.6, each divided by 2 (PF) =
0.78 to 1.3. One cockatrice wanders
6. Convert decimals: Average hp = 22.5,
multiplied by 0.78 and 1.3. The cocka-
trice has 18-29 hp.

Or maybe your guys are higher level?

"C. High-level party; size = 4, TPL 132,
APL 34
Situation #1: Wandering encounter
1. Impact desired: Easy opponent, Minor
2. HD of one monster: 30-50% APL, or
10.2 to 17, average = 13.6. Monster
chosen: cloud giant (HD 13*).
3. Power Factor: 1 (may be ignored).
4. Total monster HD: 20-30% TPL, or
26.4 to 39.6.
5. Number appearing: 26.4/13 to 39.6/
13, or 2.03 to 3.04; 2-3 giants wander
6. Convert decimals: Average hp = 58.5;
the 2-3 cloud giants have a total of
119-178 hp (each with 13-104 hp).

So you want a minor hazard for your 4 PCs who average 34th level and total 132 levels (actually 132/4 = 33rd average level) - turns out 2-3 cloud giants will do, mathematically. #2 is "minor placed encounter" with a potentially 160 HP red dragon. You know you've hit the big time when math says dragons are minor fights.

It also has advice on using this on the fly to make an encounter match the PCs better on the fly - instead of changing die rolls, change the monsters. "I make up results regularly, to keep the game fun - and isn't that why we're all playing?"

I always think of that when I hear gripes about "balanced encounters." Making all of this a mathematical thing happened in print as early as September 1985. That's even before I stopped playing AD&D and moved fully on to Rolemaster and GURPS (and then just GURPS.) It's a workable system, too, if more mathematically heavy than other systems I've seen for balance. If you play a D&D-based system, by which I mean BECMI or B/X, this system works very smoothly. It might be worth a look if you can find Dragon #101.*

* I bought that Dragon Archive back in the day so I'm lucky, there.


  1. I really like these two posts back-to-back. I took the idea of balance from yesterday's Gygaxian comment to mean the encounter was presented so that player skill can intervene and give the players a chance to make the call to flee if overmatched (ie, new players with first level characters wouldn't even know what an Invisible Stalker is, let alone that it's time to run...) But not necessarily implying every fight could be won through melee. Whereas the Mentzer article from today is clearly pointing towards using math to create balanced encounters from the perspective that every fight can be won with strength of arms - something we decry as a "new school mindset", but apparently hearkens back to 1985 !! I had no idea. Nice find Peter; are you just jumping around old Dragons for inspiration?

    1. I agree that's one way to look at it. I read it more broadly, that it's about making sure you're not overmatched. So no invisible stalkers or (fill in whatever powerful monster) because you've got no answer to that - none of the options works, even if you're a veteran player.

      Frank Mentzer is really showing something that Len Lakofka showed so often and Delta's D&D shows so often - you can ram all of the numbers of D&D into a spreadsheet and have it give you the average results of X vs. Y, or option A vs. option B. He's just applying it systematically to monsters. It's not really all that much different than the idea of placing monsters by level, either, it just allows you to measure more consistently and precisely what a monster's power level is . . . and how numbers on either side affect that. In a way, it's odd that it took 10 years to see this kind of thing in print - the numbers needed to do this math were always there.

      I've been meaning to post about this for a while. I actually thought I did, but I couldn't find it when I went to link to it yesterday. So I went ahead and wrote a post about it today. I just remembered this existed - for a while, I was a Dragons subscriber and read everything in every issue, so I can often remember something is out there just because it was part of my formative experience in gaming.

    2. Agreed! I tend to see "encounter design" systems such as this one as a tool for the GM to make sure the encounter is as hard as intended. They tell you what a "balanced fight" looks like, but they never force you to make every fight balanced, or every encounter a fight.

      You can use them to make nuisance fights, you can use them to make meatgrinders best avoided. Their real utility lies in helping you make sure the nuisance isn't a meatgrinder in disguise, or vice-versa. One can get an instinctive feel for it with years of experience, but a good design system means one doesn't have to.


Related Posts Plugin for WordPress, Blogger...