Converting Monsters From D&D

Converting Monsters From D&D

Back in the day, Steve Jackson wrote an article for Space Gamer #56 that discussed how to convert D&D monsters to The Fantasy Trip. That classic article is a great start, but there is more to making monsters come to life in TFT–a lot more.

Where To Start?

The genesis of this article is one that Steve Jackson wrote for the Space Gamer magazine back in the day. The original article talked about how to convert D&D monsters into TFT terms. It was a great article, and I highly encourage everyone to read it. The majority of the next section comes from that article.

However, before trying to convert a monster from OD&D, AD&D or any other d20-based game, first take a look at what is there already. Start with The Fantasy Trip:In The Labyrinth (TFT:ITL). Look for a creature already included there, or one that is similar. One you can modify to be what you want. That is the easiest way to find what you are looking for.

Other places to look for existing or similar monsters are the adventure supplements that Metagaming put out–Silver Dragon, Unicorn Gold, etc. An even better place to find more creatures is C. R. Brandon’s Heroes & Other Worlds game. He has done a lot of great work already, converting a number of classic beasts to something very similar to TFT.

On To the Stats

However… If you can’t find the creature you want in the existing sources, or one close to them, use these guidelines to convert from D&D to TFT. The stats listed here are from the original AD&D Monster Manual.

Frequency & Number Appearing. These are general guidelines for how rare the creature is, and how social they are. Use, alter or ignore them to suit your campaign world and situation.

Armor Class. This is one of the trickier stats to convert. D&D uses AC as a general way to determine how hard a creature is to hurt–both to hit and cause to damage to. In d20-type games, AC starts at 9 or 10, depending on whether you use descending or ascending armor classes, and either increases or decreases with protection or difficulty to hit.

So–start with 9 or 10. This represents the equivalent of a normal human body–soft flesh with no protection, and a relatively average difficulty to hit. Consider that the natural AC of the creature. This is based on the relative toughness and natural armor of the creature. Look in the table below to estimate something equivalent:

Armor Class (AAC) Armor Equivalent Hits Stopped
AC 9 (10) Soft body without protection. 0
AC 8 (11) Thin chitin, light fur, cloth armor, shield only. 1
AC 7 (12) Leather armor, medium fur or light scales. 2
AC 6 (13) Leather armor + shield, heavier fur or scales. 3
AC 5 (14) Chainmail armor or heavy reptile scales. 3
AC 4 (15) Chainmail armor + shield or medium dragon scales. 4
AC 3 (16) Plate armor or shell. 5
AC 2 (17) Plate armor + shield, heavy shell. 6
AC 1 (18) Old dragon scales. 7

Select a natural AC from the table, and use the Hits Stopped figure as the monster’s armor protection.

Now, look at the actual AC given by the D&D stats. The difference between the natural and actual AC has to be accounted for, either by magical ability or the creature’s natural evasiveness. This will be done by a to-hit DX adjustment.

Subtract the actual AC from the natural AC. If using Ascending Armor Classes, subtract the natural from the actual instead. If the difference is 1, ignore it. If it is more than 1, divide the difference by 2, rounding up. Use this as a DX adjustment for an attacker.

For example, if a creature’s natural AC is 6, and the stats list 3, assign a penalty to hit of 6 – 3 = 3, 3 / 2 = 1.5. Rounding up, this would be a -2 adjDX to hit.

You don’t have to, but you really should explain that difference somehow. Maybe the creature is small. Maybe it is fast. Maybe it is magical and tough. The point is to make that creature more than a simple stat.

Move. To determine the MA of the monster from the D&D Move, compare the creature to a normal humanoid MA of 8, 10 or 12. If the creature is slower, assign an MA below 8. For a faster creature, assign one above 12. Keep the MA an even number. Also, remember that creatures may have ground, water or air speeds. Compare to other similar creatures in TFT:ITL. If all else fails, consider an MA of 1 per 10” of D&D movement.

Hit Dice. Hit dice determines the number of hits a monster can take before it dies. This is another tricky one. D&D bases the hits on rolls of a number of d6, which leads to a wide range of possible numbers–more than feasible for TFT. The problem is that as monsters increase in hit dice, a simple conversion would mean their ST would skyrocket. To convert that to a ST range that can be useful for TFT, use the following:

Get the average D&D hit points for the monster by multiplying the hit dice by 3.5, then…
1 or 2 hit dice: Multiply average hit points by 3 to get average ST.
3 or 4 hit dice: Multiple average hit points by 2.5 to get average ST.
5 or 6 hit dice: Multiply average hit points by 2 to get average ST.
7 or more hit dice: Multiple average hit points by 1.5 to get average ST.

Keep in mind many modern OSR games use d8 or even d10 for creatures. These are also the average for that creature. You can always raise or lower the ST figure some as you see fit. Again–check against comparable existing creatures.

% In Lair. This is another stat that depends entirely on your world.

Treasure Type. D&D uses random tables to determine what treasure a monster might have. (I always thought that kind of odd–I can see that as a way to describe a creature that the reader might have no concept of… But then why not just describe its treasure levels explicitly?)

Use these tables as a starting point to get an idea of what treasure the monster is likely to have, then adjust for your campaign and situation. Be creative.

Number of Attacks. This is a stat that can be taken as written. The only caveat would be in making the creature too powerful–use discretion.

Damage/Attack. This is another tough stat to convert. Look at the numbers listed for D&D, determine the type of die to use, and convert to d6 by fudging the average and total range.

The averages for each poly dice are:
d4: 2.5
d6: 3.5
d8: 4.5
d10: 5.5
d20: 10.5

So for example, a monster that lists 2-20 would be 2d10. This would have an average of 11. This could be approximated by anything from 3d6-1 to 3d6+2. Don’t sweat it too much. Use your best judgement and eyeball it.

Special Attacks & Special Defenses. This could be anything from magical attacks to other abilities. Look for TFT spells that are close to the desired abilities and go from there. Make it interesting!

Magic Resistance. This is only rarely found in TFT. Feel free to ignore it, or use the monster’s special defense here.

Intelligence. Convert intelligence by using the following guidelines from TFT:
IQ 0: Non-intelligent.
IQ 4: Reptiles.
IQ 5: Most mammals.
IQ 6: Intelligent animals.
IQ 7: Semi-intelligence, such as apes.
IQ 8 or 9: Low real intelligence.
IQ 10 or 11: Average humanoid intelligence.
IQ 12 to 14: Very intelligent.
IQ 15 to 18: Highly intelligent.
IQ 19+: Super intelligent.

Alignment. This is another stat not used in TFT. Use as a guideline for general behavior. Keep in mind that most monsters will just want to be left alone–or be hungry. (See below).

Size. Allow 1 hex for each 3 feet of height or length given in D&D. Again, compare to existing creatures to get a feel for how many hexes the new one should be.

Psionic Ability. Yet another stat not used in TFT. Treat as a magical ability, with or without ST cost. Make it interesting.

DX. This is given for D&D characters, but not really used for monsters in combat. The best way to determine DX is to use the following table to see how often the monster could hit:

DX Probability to Hit Notes
6 9.2% Lowest possible DX where a creature has any hope of hitting in combat.
7 16.2%
8 25.9% Clumsy humanoid.
9 37.5% Starting to be dangerous.
10 50% Hits exactly half the time.
11 62.5%
12 74% This is comparable to a good, seasoned fighter.
13 83.8% Now the creature is starting to become formidable.
14 90.7% Deadly. This creature would almost always hit, and if it does any damage…
15 95.4%
16 *** 16 or more is a automatic or critical miss. Any DX above this is only useful when there are DX adjustments.

Take a look at similar creatures for their DX, then pick what looks best. Remember: If a monster hits frequently, and does any amount of damage–it is going to be deadly.

And that is it for the classic D&D stats. I would not mess with the Hit Dice Equivalent or XP stats–just use TFT rules and run with it.

Breathing Life Into Them…

Now what? Well, the trouble with straight stats conversions is that there is so much left that can be done to really bring the monster to life for the players. This is where modern games and their bestiaries have improved on the basic stats listing of the original games.

Many games and authors have put a LOT of effort into improving the descriptions of their monsters or creatures. This includes a more full description of the monster, from its looks and smells, to its ecology to how it acts. (On the other hand, the Swords & Wizardry WhiteBox rules goes as far as saying that rules should give as little description as possible–let the GM’s creativity determine those details).

I think the best way to breathe life into monsters really is in their descriptions. Unless the characters have encountered the creature or race before, describe them. Don’t just say “a ghoul,” but rather say “a disheveled creature, with pasty skin, large white eyes and a disgusting, charnel house smell”–something like that.

Another way to improve monsters is to describe their ecology in better terms. Describing where a monster lives and how it inhabits the world around it goes a long way to allowing the GM to place the creature in his campaign world in a logical and realistic manner.

Details that would really help include:

  • Where the monster can be found. Many games do this with categories like Plains, Forest, Jungle, Water, etc.
  • How social the monster is. This ties back to the D&D stat for Number Appearing. On one hand it is important for combat situations, but it is also an indicator of how the creature lives.
  • What its typical lair looks like. Is the lair a building, like a humanoid would live in? Is it a cave? Does it live in a tree?
  • The creature’s usual diet. Is the creature a herbivore, carnivore or omnivore? Or does it feed off of others’ souls?
  • How big of an area that the creature requires to live. This can be very important. A dragon will need a much larger area to support it than a wolf.

Better descriptions of the tactics that a given monster or creature would use are also things that can help bring a monster to life, too. Does the creature simply attack, or run away? Does it use pack tactics, or operate singly? What are the details of how it uses a special weapon like a petrifying gaze? Just saying that creatures have certain capabilities is not enough.

(With all of that being said, I have copied all of the creatures in the original Flora & Fauna section of TFT:ITL into the Bestiary section of this site. I will be updating the entries for each creature to include information like this over time. I will also be converting monsters from D&D and other sources and putting them in the Bestiary, too).

So–what do you think? Are there better ways to convert D&D monsters, or tweak their listings to better suit today’s gaming–or just Old School TFT?

PS. Yes, this is the third and final cover of an AD&D manual that I will use on this site!

Marko ∞


  1. Sorry for the weird look of the email, folks. I fixed the error in the article and it looks much easier to read now!

  2. I think this may be the best single article you’ve done yet! There’s a LOT of behind the scenes work that went into this one (I speak as someone who’s tried to do something similar in the past), even though it may not look like it to the casual reader, and I *really* appreciate you taking the time to do it! This is one I’m printing off and adding to my TFT publications stack! ;-)

    The one comment I will make regarding C.R. Brandon’s HOW version of the Monster Manual is that he’s made the D&D monsters VERY deadly — even the ones that a beginning D&D character would tend to shrug off can be extremely dangerous in TFT terms, and the tougher ones are virtually impossible for even a group of adventurers to defeat. If anyone plans on using them, I’d give serious attention to “nerfing” them a bit to get the results more in line with D&D results so that your players aren’t losing characters hand over fist… Taking a look at HOW’s version as compared with the D&D version and then converting the D&D version using the standards in this article and comparing the result with HOW, should give you a good feel for how to proceed using HOW stats… Of course, some of you may prefer everything to be very deadly — you pays your money and you takes your choice!

  3. Thanks, Jeff, but I have to say most of the heavy lifting was done by Steve Jackson himself in the original Space Gamer article. I embellished.

    I agree, too—TFT is much more deadly than D&D. I am all for letting players pay for sins of stupidity, but you have to adjust monsters based on characters’ abilities. Slaughters are no fun!

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