Monte-Carlo Measures of Monster Levels, Pt. 6

Six levels of monster tables in OD&D, and six posts discussing the details of monster special abilities (so far). Let's see what happens at the top end of the tables (data here):

High Level Fighters: One possible wobble in our simulator is that Fighters stop getting full Hit Dice after level 9, so the baseline of pure Hit Dice comparisons (Equivalent Hit Dice, EHD) might be a bit biased after this point. But the effect should be fairly minor; fighter Hit Dice here are d8's by Sup-I rules (expectation 4.5), abilities are straight 3d6 (so no Constitution bonus on average), and I award 3 hit points per level after 9th (end result: only a 1.5 pip difference between lower levels and higher levels). Plus, fighters continue to get normal improvements to attack chances at higher levels. Perhaps if we were completely precise we should reduce EHD by 1/3 for each level after 9th (so: Medusae would by EHD 11, Balrogs would be EHD 18, a slight modification from our table).

Chimeras and Gorgons: Both of these have a deadly breath weapon that places them solidly in the Level 6 table (the former, 3d6 fire damage; the latter, petrification). Each is an area attack, of course, so subjectively we could boost their EHD even higher for having the capacity to take out multiple opponents at once. Note that in OD&D, no specification was given for how often they can use these attack forms, or at what frequency. It seemed elegant to me when coding them to use the exact same method as for Dragons; up to three times per day, with a roll of 2d6 ≥ 7 (58%) indicating breath instead of standard attacks. The range of the breath is stated, 5" or 6", that is, about half to two-thirds that of a Red Dragon.

Vampires: The blood-drinking master undead have a veritable Fibber McGee's closet of special abilities, more than twice as many as any other monster type -- flying, magic-to-hit, energy drain, regeneration, charm person, summoning, and polymorph (as well as the well-known special vulnerabilities to keep in mind). The Arena simulator makes use of the energy drain, regeneration, and even charm person (the vampire gets an initial entry gaze attack with −2 save modifier, but I assume that if saved that the fighter is then immune and doesn't have to avert gaze thereafter). The magic-to-hit defense is a non-issue, since our fighters (surely of this level) are all assumed to have a +1 sword. The flying is not simulated (nor is any specific movement). Neither is the polymorph or summoning; the former is mostly just a retreat mechanism, while the latter (10-100 rats or 3-18 wolves) would break the current program architecture in expecting just 1-on-1 fights in the Arena. This could have been a notable factor, but of course these are very low-powered helper monsters in any event. (What's your guess? We'll see in Arena v.108.)

All told, Vampires are assessed at EHD 15, just about double their actual HD 8, so doubling the XP for their special abilities (at least) is definitely justified.

Dragons: As with Lycanthropes and Giants, I tried to pick the one most representative type for my data input; in this case, a smaller Red Dragon of 9 HD, which puts it at about the median of available Hit Dice points for Dragons. Hit points are rolled as per the book: a single d6 indicates age level and hence uniform hit points for each HD (so either 9 hp or 54 hp are as likely as anything in between); note that this makes the variance in hit points tremendously greater than for other monsters (who otherwise have bell-shaped distribution with the most likely hit points around the median). The functioning of the fire breath is explicit in terms of frequency and maximum usage (see Chimeras/Gorgons above).

I interpret the damage from that breath in the harshest terms, that is, always equal to Dragon's maximum hit points no matter how much damage it has taken (as opposed to Moldvay Basic D&D where the current hit points is the damage output, so much less dangerous after a few rounds of hacking it down). I don't give their claw/bite routine the many dice of damage suggested in Sup-I, but I do give 2 attacks for 2 dice each here (or in practice, 1 bite for 2d6 and 2 claws for 1d6 each, mathematically the same). Of course, it was always a bit wonky that the youngest 9 hp Dragon, and the oldest 54 hp dragon, both have the same attacks, damage, saves, and to-hit under these rules (the AD&D Monster Manual slightly adjusted this for the saves, not the other factors), but this is maintained as-written in the Arena simulator.

So, for the case of Dragons it makes sense to do a run for each of the separate Age categories and see how our model measures them (again, mid-level 9 HD dragon in each case):

So, we see that even a Very Young dragon with 9 hit points is an even match for a 6th level fighter; if it gets initiative it can tear into a man and do several dice of damage (4d6 in this interpretation; and it also has the best armor in the game to this point, as plate & shield, AC 2). A Very Old dragon with 54 hit points is assessed the same as a 45th level fighter (!), although with pro-rated-hit-dice adjustment, we might call that only around 33rd level to be nice. And recall that our baseline fighters still only have straight-3d6 stats, chain & shield, and a single +1 sword, no matter their level; more well-equipped fighters will be better off against this challenge. But still, getting hit by 54-damage fire breath a few times in a row will pretty much ruin your day no matter who you are.

And keep in mind again that the breath weapon is also an area attack that can probably torch a whole party if the lone fighter brought any friends, so feel free to discuss how many more EHD's should be added to account for that. Clearly the XP could be doubled, tripled, quadrupled, or more over the base HD, depending on age category.

Balrogs: Yes, Virginia, OD&D originally had Balrogs in the core rules (and in fact, they're probably referenced as an example throughout the little brown books more times than any other monster), before they were taken out from printings after the 1st. See the Balrog Reference Sheet generously provided by Zenopus Archives if you want to fill in that gap for your game. The Balrog has flight, top-level armor (AC 2), a magic sword and whip, among the most Hit Dice in the game (HD 10), a special immolation attack, and also the first instance of Magic Resistance in the game of D&D (though not simulated here, since it makes no difference against our non-spell-casting fighter opponents). They get two attacks, which here I assume get 2d6 damage each (Sup-I says 1-12 points for the sword); my ruling on the whip/immolation is that the whip can strike for 2d6 damage normally, and on a hit then we also check 2d6 ≥ 7 to see if the target is pulled into the Balrog's immolating body for an extra 3d6 fire damage (the average size), save for half. The Arena simulator says this combination is worth EHD 22, again about double the base HD of 10 (and somewhat more dangerous than the average mid-level Dragon). Note that by the book's Wilderness random encounter tables, you might run into 1d6 Balrogs just wandering around together on any given day; giants truly walked the earth then, and lifespans were indeed very much shorter.

Any interpretations here that burn your britches? Still worse things to come.


  1. Beneath the trees where nobody sees, they swallow souls as long as they please.
    Cuz thats the way the Balrogs have their piiiiiicnic!
    Sorry for the OT, but I had to get that out of my head.

    1. That's awesome! :-)

      If Balrogs come up in my game, they will probably be having a picnic now.

  2. It has been interesting how many ambiguities you had to resolve in order to explain monster abilities well enough to a computer for them to be emulated.

    Makes for a hot list of sharp edges in the system.

    1. I agree, I think that was the most interesting part of the project, actually.

  3. I feel like your results for dragons are actually an argument in favor of the breath-damage-equals-current-HP interpretation. That's a change that would have more impact as the dragon's base HP increase, not only because it means later breaths will be doing far less damage, but also because the more HP a dragon has, the more time it will spend alive and breathing reduced breaths.

    I also like the idea of a party questing for dragon lore, discovering that the breath gets weaker as they're injured, and then when they encounter a real dragon, desperately trying to hurt it enough to survive the next blast.

    1. I can see that argument. I'm not that dogmatic about it, but I think I narrowly feel like having the fight progressively raise tension (PC hps go down to where dragon breath might finish them off), instead of reduce tension, is a good dramatic gesture.