I'm writing a monster compendium that focuses on the lore of creatures, such as their behavior, habitat, and mythology, rather than on game mechanics. However, I'd like to include basic stats for each creature to allow for easy adaptation into various RPG systems.

Some stats are obvious, like Size, Speed and Number Encountered. Others that I find easy enough are:

  • Intelligence: Null (0), Very Low, Low, Subpar, Average, Decent, Good, High, Very High, Excellent, Superb (10)
  • Strength: similar to above
  • Perception: similar to above
  • Reaction: Categories like Territorial, Aggresive, Cautious, Fearful, Inquisite, Friendly, Furious

I'm finding it challenging to define the following:

  • Defense: Should I list resistances or assign an armor class-like grade?
  • Offense: Should I list possible attacks (e.g., bite, claw) and assign a grade from 0 to 10? Should I include potential damage?
  • Skills: Should I include specific abilities like Pack Tactics, Desert Survival, Acute Vision, Climbing, and grade them?

My objectives are:

  • To establish a clear hierarchy of danger among the creatures (e.g., a mammoth is more dangerous than a moa bird).
  • To facilitate the conversion of these stats to other game systems, potentially by providing a conversion method in the Appendix.

Are these stats straightforward enough to meet my goals?

  • 16
    \$\begingroup\$ You are trying to do something fundamentally impossible. The act of codifying stats by definition creates [at least part of] an implied system. \$\endgroup\$
    – Novak
    Commented Nov 11, 2023 at 21:50
  • 1
    \$\begingroup\$ This question seems like it's asking how to create a useful taxonomy that can then be subsequently interpreted by a game system. What are some of the specific systems that you are going to use this compendium with? \$\endgroup\$
    – GcL
    Commented Nov 14, 2023 at 0:40

4 Answers 4


Focus on concepts, not on statistics

It's not that system agnostic monster handbooks cannot be made, in fact there are successful examples, that you could use as inspiration. But I think you should focus on interesting creature concepts, rather than game mechanics.

Monster statistics of various systems are inherently tied to the system mechanics. Systems with conceptually different mechanics or target play experiences will treat the same idea very differently.

For a simple example, let's take resistance to non-magical damage. Even within D&D, this has changed over editions. In 1e/2e, monsters were either fully immune to damage, or fully affected. In 3e, resistance was a numerical value that got deducted from damage, and in 5e, resistance halves all damage, and immunity entirely negates it. So the very same demon would behave very differently in those different systems. Nevermind monsters that cast spells or have spell-like effects.

Secondly, some games are designed for gritty, deadly combat with things like hit locations and no level-dependent hit points (for example, old Runequest), others like D&D have much more abstracted and simplistic combat systems and ample healing that encourage heroic, fast combat (like D&D). Because these systems play very differently, you cannot just plunk the same monsters in there and expect them to work.

Lastly, because a lot of the real work is in translating a creature concept like "floating ball with tentacled eyestalks that shot magic rays", or "troll" from the generic features like if they are strong, regenerate damage and so on into actual game mechanics that follow the systems internal logic, such a monster manual would still leave most of the conversion work to the GM. At that point, you can just grab the D&D monster manual, or the Call of Cthulhu one or whatever, and translate those monsters directly — you also have all the information if they are very strong, fast, resistant or regenerating right there, and it is no more work than translating from your new "generic" system.

  • 2
    \$\begingroup\$ I've never seen anything like Fire on the Velvet Horizon. Thanks for the offhand exposure. \$\endgroup\$
    – order
    Commented Nov 10, 2023 at 23:22
  • 2
    \$\begingroup\$ And some (like the Forged in the Dark set) have no real stats at all on enemies and largely abstract combat. \$\endgroup\$ Commented Nov 10, 2023 at 23:45

Provide relative terms that are likely to appear in most systems

One approach is to provide the descriptions in a way that refers to items that will appear in most systems. If you say, "The hide is as difficult to pierce as Full Plate" then that will translate relatively well to any system which uses Full Plate as an armor, which includes most fantasy systems. Since Full Plate is something that exists in the real world, it is still providing a solid baseline that someone using a system without full plate can probably find something roughly equivalent and use those statistics in their chosen system [Small caveat: Armor in the real world was complex and changed over time. There were many things called full plate and many other things that distinctly did not use that name but would be modeled that way in most games, but it still gives your average player a baseline to work from.]

Similarly for offense, if you say "The bite is as damaging as being stabbed by a dagger" or "The gargantuan claws tear through material as well as a long sword" then that is easy to convert since most systems have those as concepts. [Same caveat. If anything, that is more complex. There were many things in the real world with names that roughly translate to "long sword" that were very different from each other, but it is still a solid baseline to work from, especially in games that have a stat block for "long sword"]

As for special skills and abilities, you should definitely mention them. Real world animal descriptions often include things like that. Just look at some real world wikipedia articles on animals. In an RPG, it is even more important to know.

I would shy away from capitalizing them the way you did in your question though. Capitalizing a word in that way in an RPG text (or for that matter, most legal texts) implies that it has a very precise definition and that the precise definition is located in the same text or in a text directly referenced. If you say they use "Pack Tactics", then I assume that somewhere in that book there will be a very specific definition for exactly what that means. In D&D 5e for instance, there is a very detailed and exact definition for that specific phrase. On the other hand, if you say "They are pack hunters" then I will think that if I want to import this into a system, I should think about what that would mean in the system. In D&D, it would probably translate into Pack Tactics. But in another system, it just might mean I should usually plan to include more than one of them in an encounter, and in Exalted I might model them as a battle group, perhaps with free benefit of a war charm.


You should have no trouble describing your creatures without any reference to a System, or even system-related concepts like "stats" or "attributes". Just describe them like you would when writing a fantasy or scifi book, with as much detail as you can think of.

First of all, a GM who opts to use this kind of bestiary (instead of one tailor-made to a specific game system) will easily be able to work with that. First of all, they will in practice tune the individual encounter to the relative power level of their current band of adventurers, anyways, if only by adjusting through the number of individual creatures per encounter, if not by opting to ignore some of their capabilities or fudging the stats behind their secrecy screen.

Second of all, the GM needs to grok the severity of the create anyways to be able to represent it to their players, unrelated to numbers. So the descriptive bits you are providing are much more important than any numbers, in any case. A super-deadly monster might be more effective if it's just a rumour, or if the heroes just get a short blurred glimpse of it in a storm at night (think about the original "Alien" movie and its depiction of the enemy). So the players will for sure don't know any of the stats, and the GM will relatively easily be able to come up with stats by comparing with known creates from the official bestiary of his system (or others from your bestiary).

One awesome way could be to provide, aside from the objective description of your creatures, a short (one or a few paragraphs) scene involving, say, a bunch of heroes fighting against the creature, or describing how it decimated a kingdom all by its own, or how the creature is a harmless staple in any village, known for it's benevolent features, or anything like that.

If you need inspiration, one of my absolutely favourite author of (non-roleplaying related) fiction involving such kinds of description is Neal Asher. His SciFi books almost always contain planets or ecosystems with weird and wonderful (and almost always extremely deadly) fauna, and he has a real knack of describing them in only a few paragraphs from the point of view of other characters. If you are at all into SciFi, I'd highly recommend to check them out (as I said, almost all the stories are like this, but specifically you could look for the "Spatterjay" series, or check out the anthologies of his short(er) stories).


Option 1: The real world is system agnostic

Write it like you would write an entry about a real world creature. So for example look at how entries in various (non RPG) books are written about brown bears, elephants and tigers and do likewise.

Option 2: Write the entries in world

Write your entries from the perspective of an "in world" wildlife researcher. How he percieved the creature, what he observed them doing, what was exceptional about their physique or behaviour. How they interacted with him or others.
For really dangerous creatures you could instead write eye witness reports from survivours or remnants of diaries that end mid sentence.

A dire bear doesn't have "high strength" and "a very high sense of scent", but rather: "I observed a dire bear flip a dead tree to get to its prey hiding underneath. From it's sniffeling prior to the action I took that it tracked that prey by scent much like a wolf would. After noticing me it stood up to its full size but it didn't go after me as I retreated but rather back to its feast.


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