All right, I have a question about creating a world and populating it with appropriate monsters, etc.

I created a world a little while back, loosely based off of the world found in Michael Stackpole's "A Hero Born". Did the timeline, created the history, fractional events, etc. Mapped all the major topographical features, then populated it on a semi random basis (Most of this from the World Builders Guide), and ran it past a power gamer friend of mine, who absolutely picked it apart. "This monster was in Dragon #242, and wouldn't appear here with this other monster from MMII, and this monster was in MMI and doesn't appear in the 3.5 world", etc etc.

For a nascent DM, it was rather disheartening and intimidating. However, looking at some other worlds on the 'net, it appears that the license is pretty much whatever you want to do.

What's the correct or accepted way to populate a world without continuity issues for those that would know? What's the worst that happens if you mix monsters from various editions (2e, 3, 3.5, etc) into one world?


4 Answers 4


It depends. What are you trying to achieve?

As the author of the campaign, you have a tremendous amount of freedom to create whatever world you wish to. You don't have to stick with the world created in the books any more than you want to. In many years of playing I have spent far more time playing in "generic fantasy world populated from the Monster Manual" than I have in Faerun or Greyhawk.

If you wish to write your own world, loosely based on the ones published by WotC (or others), you have the power to do that. There is no grand committee that will penalize you for straying too far from published canon :)

On the other hand, role playing is inherently a social hobby. If your players are big fans of Faerun or Eberron, and they expect to be playing in Faerun or Eberron, and you deliver something else, they may be distracted by the difference.

Figure out what your group's expectations are (usually by talking to them), and meld them with your own. Most players who have a problem with deviating from canon only have an issue because they came in expecting something different than what they got. Tell them up front that they're playing in a custom creation and give it an identity of its own and they'll be much more accepting of it.

Technical Issues

There are some things to be aware of that could inherently cause problems. Creatures from different eras may play much differently from each other. Obviously creatures from the "wrong edition" will need to have their stats translated to the game you're playing. But in addition to this there is a big mechanical difference between creatures from the 4th Edition Monster Manual I and Monster Manual III. Creatures from one need adjusting to be compatible with creatures from another.

Verisimilitude Issues

Sometimes when building a world you might miss something that just doesn't make sense. Why are the Chaotic Evil Dogeaters living right next door to the Lawful Good Puppylovers? Shouldn't there be more conflict there? Why not? These issues are easy for an author to overlook (there may even be a reason for it, just not communicated fully).


Boiling this down to bullet points:

  • Are you trying to match canon, or create your own world? Or a mixture of the two? Either way, communicate that to your players. Giving your setting an identity and a name helps with this if you're setting out on your own.

  • Ask your friend to explain each of the issues he's come up with. Is the issue a problem you care about? If yes, fix it. If not, move on to the next one.

  • Good luck, and have fun.


The following epilogues are based on the comments that have come and gone since this answer was first posted. Comments were distilled solely to present my own point of view, and all quotations should be taken with a grain of salt ;)

Epilogue 1 — I'm the DM, Do What I Say

A DM's world and monsters don't have to be justified, and a player who demands or expects it is a control freak who needs to sit back down in their player-chair.


Players who hold the MM over the DM's head can jump off a cliff as far as I'm concerned. I see it as a fundamental courtesy to the one running the game, and a pretty severe social courtesy to violate. Players who demand that the MM to be an inviolate reference manual for monster-killing deserve to have their plans backfire.

The key to what I'm trying to say here is communication. As the DM, you absolutely have the right to create your own world from the ground up. You can use the monster manuals, not use the monster manuals, use parts of them, whatever it is you want to do.

But it's important to understand that not everyone expects to play that way. And when people come into the game expecting one thing, and get something very different, they often react in negative ways (for reasons that are very human).

I see no real reason to pull the "I'm the DM, so do what I say" card. I don't think I've met a player who wasn't cool with a homebrew setting when told that that's what they were getting. This is something that's trivial with communication and a potential landmine without it. There's no reason to take the hard way here, even if it is "right."

Now, if you've decided to run an "off-book" setting, AND you've told the players, AND you have a group that wants to run that (and you should! Most groups will) AND someone is still giving you grief... THEN it's time to lay down the law.

Epilogue 2 — Playstyles

It depends on playstyle then, by what means that's communicated. My current game features many lessons that are available character-post-humously and I've yet to see a player take any dangerous situation for granted, or assume that they can know undiscovered things before discovering them.

This is very much a play style thing.

Some people like to play as though they themselves have been transported to an alien world where everything is new and waiting to be explored.

Others like to play like their characters are a part of the world, and have accumulated experience and knowledge.

Both styles are good, and can even be mixed-and-matched, but if your group isn't on the same page people can get angsty pretty quickly.

For players who expect their characters to be a part of the world, setting knowledge is what gives player characters autonomy, and allows them to take action beyond what the DM tells them.

Like rules lawyers, most of the players who bring it up do so in a jerkish and overly-entitled way, but that doesn't mean there isn't a grain of truth to what they're complaining about.

Again, simply communicating and demonstrating that you periodically change things is enough to defuse the situation and put players in an investigative mode.

Epilogue 3 — Monster Knowledge

The way I deal with players who wish to have experience and knowledge is a skill Knowledge: Monsters or such. It uses game mechanics, lets them identify even homebrew monsters if they want to, and gives them valuable data to work with without breaking the believability...at least somewhat. It was actually one of my players who came up with this skill, asking for it, and it turned out great.

Monster knowledge skill checks are a pretty great way of pushing customized exposition to the players. And latter editions of D&D have extensive knowledge check systems baked in.

But... A skill check requires an explicit stop, realize information is missing, query DM, make skill check, get exposition cycle. It works great if your players know they're dealing with a custom world, and fails spectacularly if they think "Faerun; got it," make a plan, and have the rug pulled out from under them.


Your player is giving you bad advice — ignore him.

Your world works how you want it to.

Neither of the critiques you cited from your powergamer make a bit of sense at all. "That's a 1e monster it wouldn't be in a 3.5e world" has no merit — people have ported absolutely every monster forward, and what edition they have rules for is totally separate from whether they inhabit the fictional world. "Those monsters wouldn't be found together" is marginally more coherent, though a) maybe those two races aren't enemies in your world regardless of what the MM says, b) maybe those two races are indeed at war and that's why they're in the same county (as it's hard to have enmity if you always live on opposite sides of the continent) or c) maybe they're exceptions to the rule.

Mixing "monsters from different versions" is no problem whatsoever; at worst you need to port the stats but often that's not necessary (no fight, no stats!). You're letting this guy make you doubt yourself.

  • 7
    \$\begingroup\$ It's your world, your story, you put whatever you like in it. \$\endgroup\$
    – Joe
    Jul 11, 2012 at 0:35

Question: How do you kill a vampire?

Answer: Any way you like: they do not exist!!!

So, provided you have an in-world reason for creature $critter to have either $ability or be at $location then you are right. Sure, vampires can be gay (aka homosexual) Chartreuse-drinking cretins. Sure, Dragons can be mindless evil creatures. Sure, Cthulhu maybe the saviour of humanity. Whatever rocks your boat. What matters is that there is a reason within the world for this. They should have reasons for being what they are, living where they live, and acting the way they act – evolution, magic, society, whatever…

I would be very hard pressed to have a horse riding culture living in Alpine terrain. That would require some major explaining: What are the horses living on? How can they cope with the terrain? Where did the horses come from: where they native or imported? If the latter, by whom? If the former, how?

As for your "friend"… If you really value your friendship, talk to him and get him to understand your point of view. Otherwise, find better friends.


I second everything AceCalhoon said and he said it better than I could.

But I think I can add a couple of relevant things.

I use the rulebooks for inspiration and modify relentlessly

Personally, I think homebrew has a lot of advantages. It lets the GM have more creative control, and lets the GM tailor the rules to his group and his situation.

Also, your players if they have been playing for a while are probably expert in the monsters in the Monster Manual. But a group of first level characters shouldn't be. One way to help ensure that the players have some surprises is to only use the manuals as a rough guide.

You need to communicate clearly that it is homebrew.

AceCalhoon said this, but I think it is worth emphasizing. When I GM, I always take lots of liberties with the rules and the monsters especially. But, I always make sure my players know that before they so much as make their characters.

Failing to explain ahead of time can lead to frustrated and angry players as they repeatedly get surprised in ways they did not expect to be surprised. On the other hand, if they expect to encounter variations ahead of time then it becomes a possibly interesting new dynamic. It encourages them to do in game research (really talking to the survivors of the last attack instead of just hearing "dragon with red scales" and rushing off to get fire-protection), and it encourages them to fight cautiously, ready for the monster to break out an unexpected ability.

Be ready to adjust

While certainly not perfect, most premade settings have a decent amount of verisimilitude. You of course can achieve the same or better, but that takes a lot of work. So, if one of my players points out something that really challenges the verisimilitude in a reasonable way, I always stand ready to either make up an ad-hoc explanation or even go back and change my plans.

What I mean is that if a player says something like, "But that is from Krynn and this one is from Faerun", then that doesn't really challenge the verisimilitude but highlights my deviation. I blithely respond, "And this is neither, but inspired by both."

But if a player says, to borrow from AceCalhoon's answer, "How are the Dogeaters and puppylovers living in peace?" I will try to come up with a reason or else say something like, "Did I say puppylovers? I meant kittylovers..."

It depends on playstyle

Again, AceCalhoon touched on this, but playstyle matters a lot. I'm sure its obvious from this answer I prefer a more narrative style with emphasis on plot, exploration, and discovery. By going homebrew, I can make more things to discover and tailor everything to the plot.

If you want a very tactical game, you probably do want the players to really know the exact abilities of everything they encounter. In that case, it might make more sense to stick with the manuals or else be very open, explicit, and upfront with the changes prior to the fight.

  • 2
    \$\begingroup\$ It isn't really a tactical/narrative split. Tactical games can benefit from certain kinds of surprise. And in narrative games knowing about the setting/antagonists lets players riff on the world without having to constantly check back in with the DM. Mostly it impacts the shape of the exploration axis of play; dipping into something new and foreign, or digging behind the surface of something familiar. \$\endgroup\$
    – AceCalhoon
    Jul 11, 2012 at 21:34
  • \$\begingroup\$ You are completely right. But at least amoungst the people I play with, the tactical players tend to want to know everything upfront and more narrative focus tends to want more opportunities for surprise. It is certainly not a split as you point out, but at least in my experience it does tend to have something of a correlation. \$\endgroup\$ Jul 11, 2012 at 22:59

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