Fine-tuning custom monsters in AD&D (and retro clones)

I created some monsters but I really don't have any actual clue to how much AC, hit points, spell resistance, and attack damage would be a good ballpark estimate to make them that powerful.

Armor class and spell reisistance can be roughly estimated by knowing the ability of fighters and wizards to beat them and score a hit. But what would be a decent chance to actually hit the beast? 50%? 25%? 75%?
Estimating the amount of damage the PCs can deal on a hit is harder, but as an estimate, how many rounds would be a good target for a fight to last?

In turn, how often should the attacks of the monster hit, and what would be a good amount of damage to deal given a assumed party level?

A lot of this seems to come down to play style, but does anyone have any experiences with these things and some degree of a rough idea what would be good values?

Completely unhelpful answer: depends on the role you want the monster to fulfill.

As a rough estimate, a monster will take as many hits as it has hit dice. Its AC decides the probability of melee and ranged combatants to score a hit, so the next question would be how many characters are relying on these modes and how good are they?

A (normal) monsters damage output is determined by its attack sequence (e.g., claw/claw/bite) - as long as its HD aren't too far off.

How trigger happy are the wizards (and other spellcasters) of the group? If they pull out the big guns as soon as possible, the fight can become dramatically shorter. If, on the other hand, they are spell shy or already depleted, and will stay out of combat - well you did the calculation already in the first paragraph.

I generally take a look at existing monsters and base it off them.

-Havard

havard said:

I generally take a look at existing monsters and base it off them.

-Havard

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That was also my first thought and works perfectly finde from 3rd Edition onward.

But in 1st edition AD&D, I don't even know what creatures to use as a comparison. A 1st edition balor has 8 HD and a single attack of 1d12+1. A glabrezu has 10 HD and five attacks that deal 1d12/1d12/1d3/1d3/1d4+1 damage. And it's supposed to be much weaker than the Balor.
Also, there is a table that groups monsters into categories based on their XP value (which isn't listed in the monster and needs to be first calculated, that sounds fun), and says on what Dungeon Level these creatures are likely to be encountered. But it never says at what character level a group of PCs should be able to deal with the creatures of any given Dungeon Level. Looks like it's assumed you go down a level when you feel confident that you can handle everything on the current Dungeon Level.

The most powerful demon in my campaign is supposed to be a tough fight for a group of six 12th level characters. If they attack it straight on, they should be able to defeat it, with maybe two or three of them getting killed in the process.
The weakest demon is meant to be really quite scary for a group of four 4th level characters, who would have to use trickery and traps to be able to kill it without anyone dying.
In 3rd Edition, I would simply say the weakest demon is CR 6, the most powerful demon is CR 16, and then use CR 6 and CR 16 creatures as a guideline. With AD&D, I have not the slightest idea what creature's to use as reference.

Using the number of HD as a rough guide for how many hits the creature might take sounds a good idea. With lots of 1d6 and 1d8 weapons, and few bonuses from strength or magic items, an average damage of 4 or 5 does sound quite plausible. I think I'll make some generic fighters with default gear for my setting to use them as benchmarks for how likely they are to get a hit. (Fighters do more damage, clerics and thieves hit less often, that should roughly level out for the party as a whole.)
Another thing I've been thinking of, is that damage should probably in a range that takes at least three hits to kill a wizard with average hp. A 12th level wizard would have 27 hp on average, so creatures that 12th level parties are going to fight should only do 13 damage on a hit at most. It's just not fun to be instant-killed before you even get a chance to notice that this monster packs a nasty punch.

Thanks, that's already been some pointers I shall think some more about.

There is a general trend over the course of 3e and 4e to focus on the exiciting fight or exciting encounter as the core experience of play. This culminates in the 4e design structure where the party is expected to enter into each encounter with basically the same resources so that you can design a consistant experience for each encounter.

This is not an old school or retro approach. In retro games you should expend relatively few resources on designing encounters compared to what you spend on designing dungeons and adventures. The focus is not on the individual encounter, but on the scenario as a whole. Foes are meant to be experienced in relationship to that environment and scenario, and the challenge isn't winning the encounter but doing so with the minimal expenditure of resources. To make more challenging encounters, you generally don't take the approach of making more challenging foes. Instead, you have encounters that risk shading off into each other as monsters organize their defenses. Or you put the foes in places they'd have signficant advantages. If you look at an old school module though, very little effort is spent on ensuring 'balanced encounters'.

Until your PC's get to be about 10th level, you'll not need to worry too much about making monsters challenging. If you are careful about not letting the munchkin factor get high, actually applying the rules particularly with regards to spellcasting, and your players aren't power gaming you can probably get to about 12th level without needing to worry too much about challenge. Above 12th though, almost everything in the Monster Manuals is a push over for high level PC's with expected levels of treasure. At that point, we have to start talking about level invariant attack modes and things like that.

Yora said:

But in 1st edition AD&D, I don't even know what creatures to use as a comparison. A 1st edition balor has 8 HD and a single attack of 1d12+1. A glabrezu has 10 HD and five attacks that deal 1d12/1d12/1d3/1d3/1d4+1 damage. And it's supposed to be much weaker than the Balor.

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Why do you think that a Glabrezu is supposed to be much weaker than a Balor? You think that because 3e in particular gave the fiends clear heirarchies and clear degrees of power that they really don't have in 1e. You want heirarchies, you should be looking at the entries for 'Devil'. The 1e Balor is tougher than you think, I think, because you aren't looking at it as a whole, but I think it should be clear that it's not intended as the capstone iconic 'CR 20' foe that it shows up as in 3e.

Also, there is a table that groups monsters into categories based on their XP value (which isn't listed in the monster and needs to be first calculated, that sounds fun), and says on what Dungeon Level these creatures are likely to be encountered. But it never says at what character level a group of PCs should be able to deal with the creatures of any given Dungeon Level.

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In general, dungeon level = monster level = player level. For thieves you are going to be a level or two ahead of that because rogue levels are individually less powerful, and a paladin or a multi-classed fighter/m-u is going to lag a level or so, but its pretty close.

The most powerful demon in my campaign is supposed to be a tough fight for a group of six 12th level characters. If they attack it straight on, they should be able to defeat it, with maybe two or three of them getting killed in the process.

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In general, this will only be easy to do if you keep the Unearthed Arcana out of player hands, strongly enforce rules on spellcasting (and understand them), and keep careful control of treasure in the game either by the Monster Manual + random generation method (which will usually ensure magic is rare, a lot rarer than you'd think) or by careful selection. If you don't do this, most of the fiend lords become relatively easy fights for a well prepared party sometime between 10th and 12th level. If you want something that can actually challenge a party of 12th level characters and not look like a chump, consider the scale of power of some of the nastier fiend lords in MM2. Those actually challenged Gygax's high level PC's. Many of the ones in MM1 are actually too weak, with the exception of a couple - like Orcus and Asmodeous - that are a bit one trick ponies (but its a good trick).

Using the number of HD as a rough guide for how many hits the creature might take sounds a good idea. With lots of 1d6 and 1d8 weapons, and few bonuses from strength or magic items, an average damage of 4 or 5 does sound quite plausible.

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Depends. If the PC's are able to optimize, they can produce damage levels you won't be able to believe. For example, consider the case of a double specialized fighter with gauntlets of ogre power, a belt of giant strength, and a hammer of thunderbolts. Average damage per hit is going to be around 25, with two hits per round (full BAB in 3e terms) and in general misses only on a 1 (or thereabouts). If the hammer of thunderbolts isn't available, a good two-handed sword will work nearly as well. Or consider a high level Paladin with a Holy Avenger attacking a large sized evil monster for probably not less than about 2d12+22 damage per hit. Add to that a 12th level M-U dropping 12d6 direct damage attacks that even if they are saved against will usually be doing 20+ damage to everything in the area, and a party of six 12th level+ characters will be easily dealing 150 damage or more per round unless you are very careful about it. Most single things they encounter will not survive a single round even with less optimization than I've mentioned. Most high level 1e fights are effectively over no later than the initiative roll. Surprise round and going first is just about everything.

Once you are dealing with that, then you'll need to worry about monsters not balanced against those in the MM. I can also give you advice about what you can still use from the MM to provide challenge.

One of the reasons it's hard to give you definitive advice is that power level at a given level is going to be up to you and your players. You're going to have to learn what they can handle by experience.

Another thing I've been thinking of, is that damage should probably in a range that takes at least three hits to kill a wizard with average hp. A 12th level wizard would have 27 hp on average, so creatures that 12th level parties are going to fight should only do 13 damage on a hit at most. It's just not fun to be instant-killed before you even get a chance to notice that this monster packs a nasty punch.

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That's about right, but keep in mind the above sorts of glass cannon issues.

But I want occasional enemies that are challenging. I'm not doing dungeon crawls and treasure hauls, but occasionally the PCs will have to deal with one very significant creature that raids the country or lives in the deepest catacombs under a castle. I want to be able to tell the players if it looks like a fight they can win if they are careful, or if the only option is to run and prepare a trap that keeps them way out of reach of any of the creatures attacks.

Yora said:

That was also my first thought and works perfectly finde from 3rd Edition onward.

But in 1st edition AD&D, I don't even know what creatures to use as a comparison. A 1st edition balor has 8 HD and a single attack of 1d12+1. A glabrezu has 10 HD and five attacks that deal 1d12/1d12/1d3/1d3/1d4+1 damage. And it's supposed to be much weaker than the Balor. (snip)

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The 1E Monster Manual suffers a bit from really being an OD&D product, more than an AD&D product (and probably from the unwillingness of TSR employees to point out obvious errors to EGG).

If you look at the type VI demon in Eldritch Wizardry you will see it had 8 12-sided hit dice which makes it a bit beefier. Anyway, it's easy enough to change the type V and type VI demons to 12 and 13 hit dice, respectively, to better match the implied progression.

You will also notice a major jump in the power of monsters between the first Monster Manual and Monster Manual II, the latter being a better match for AD&D rather than OD&D.

Thanks, I'll keep that in mind. How does Fiend Folio compare in that regard?

Yora said:

But I want occasional enemies that are challenging. I'm not doing dungeon crawls and treasure hauls, but occasionally the PCs will have to deal with one very significant creature that raids the country or lives in the deepest catacombs under a castle. I want to be able to tell the players if it looks like a fight they can win if they are careful, or if the only option is to run and prepare a trap that keeps them way out of reach of any of the creatures attacks.

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Hmmm... I'm taking it you are a first time retro gamer?

I'd never really thought about how hard this could be if you were accustomed to 'new style' play.

First, it's really not that old school to give players direct meta-information about the fights that they are facing. You can and should give hints that the fight is difficult through color, flavor, and setting, but outright telling them how to face a threat and how much threat it represents seems to be an attempt at making it all a game (which, I'm coming to see is how you view RPGs) rather than a simulation or narrative (or both).

You can suggest a fight is hard by...

a) Emphasizing the great size of the monster. "The head of the dragon towers above the surrounding trees."
b) Comparing the monster to what they've faced before. "You've never before seen an ogre of such size. It's muscles bulge and its torso is as round as a barrel."
c) Dramaticly describing the setting, "As you open the door of the tomb, there is an outrushing hiss of air. The sky above suddenly becomes dark, and there is a crash of thunder that causes the ground to shake. A rushing squall brings stinging cold rain as the day turns into night."
d) Providing hints: "You manage to decipher the runes embedded in the wax seals that are placed on the door. They are a warning about what lies beyond such as what might be used to seal a plague tomb. However, the chief symbol is not actually that of pestilence. The chief symbol of them is one that means 'death', particularly death associated with the use of necromantic magic. It indicates that what is behind the door is not a disease hazard, but one of dark magic. The rune is annotated by the number 5, which indicates the level or degree of hazard represented. In this case, the five indicates the possibility of death to all life in a widespread region, such as an empire or a continent."
e) By gradual transition to grander surroundings, "The fifth staircase brings you to a sort of narthex of a temple larger and grander than those that have come before. The ceiling is lost in the darkness above, and the great columns that run in a double row to either side are made from a black stone flecked with red and carved with writhing serpants."
f) By emphasizing how completely outclassed they are, "The woods around you are suddenly filled with howls as from a host of wargs. In the twilight, you can see perhaps 60 yards through the boles of the forest. In the gathering darkness, you can see dozens or scores of goblins riding loping wargs in ragged formation to your north and west. The are moving roughly to the south-west. Many bear flags streaming behind them, showing the devices and heraldry of at least a dozen clans. Bats are streaming through the forest over there heads. From the thunder of the howling wolves, the singing goblins, and the crashing of spears against shields, you feel certain that this is only the edge or vangaurd of a mighty host. "

Markers like that tell the players that they should possibly prepare for the worst, or flee, or that parlay is a better approach than combat, or that they are about to get in over their heads. But you should try to avoid actually telling the players what to do or what strategy you expect them to employ. If you do that, you run the risk of playing the game from both sides of the screen rather than letting your players choose how they want to play. Avoid linear expectations of 'they should do this, followed by this, followed by this, thereby obtaining level X so that they can face this.'

Secondly, again, you'll need to know what the particular PC's you have can face. Level alone won't tell you much. Eight 8th level PC's with treasure obtained from published adventure paths of some sort intended to force rapid leveling will be challenged by very different encounters and deem different monsters 'serious' than 4 8th level PC's with gear that has been randomly generated or carefully selected as to maintain a low pace of advancement and power acquisition. You need to know what your party is capable of. A party without a cleric is going to find wraiths and shadows very much more challenging than one that has a cleric capable of destroying shadows. A a party that has acquired skillful play skills is going to be very much more successful than one that only has straight foward close and attack strategies while dumping offensive spells in their tool bag. By the time you are DMing for a party of a given level, you should have a fair idea how much pain that they can bring per round on a typical foe with 4 AC, and conversely how much pain they'll recieve facing say 12 bugbears. You'll need to scale from what you know.