What exactly is common knowledge

[TheGogmagog]

Your first problem is declaring to your players what is common knowlege in your campaign setting. The bluebook example above or certain parts of the MM. In my opinion, The text between the stat block and combat are common knowlege. This would be given if they make the suggested Knowlege check DC 10+HD (I substitute CR if higher). As the knowlege skill suggests, for every 5 points they gain special abilities or vulnerabilities (I roll randomly).

The second problem is enforcing it. Personally, when playing with DM's or Metagamers, I will either change the monsters's vulnerabilities or compensate for them. If EVERYONE knows that the red dragons are immune to fire and vulnerable to cold, then the dragon does too. If he has a few age categories on him he had better have a ring of cold resistance.

Once you take these two steps, I don't know what you do with the people who don't follow them. Forcing someone to poision the mumy or cast fireball at the red dragon doesn't seem right. The player will resent it and it wont be fun for anyone.

That answered, I have a small rant. In cases like this you always get several posters analyzed/answer/attacks the examples you gave as if those are the only two instances where this occurs. There are plenty of cases of this that trouble me. The two big ones for me is the destruction of vampires, or lich psylactery. Are these slain enough for these to be common knowlege?

 

[Elder-Basilisk]

Actually, you're not. The rules for knowledge skills provide a way for the players to get extra information from the DM. They are most emphatically not required in order to justify not acting like a moron.

There is no requirement that PCs fumble around like idiots and let the troll regenerate and kill them all if they don't have knowledge nature. Nor is there a requirement that PCs continue using the same weapon that doesn't work against an evil outsider if none of them make the knowledge planes check. What the rules for knowledge skills do is give players who don't have the appropriate knowledge a way to get some relevant information from the DM. And that's a good thing. Otherwise, anyone without every knowledge skill would be helpless against certain kinds of monsters--and the game isn't supposed to be "the fighters fumble around doing the wrong thing until someone with knowledge as a class skill tells them what they're supposed to do."

So, whatever your players might think is "common knowledge", you are perfectly within the rules if you request a Knowledge check.

Andargor

 

[Elder-Basilisk]

And this is the kind of thing that seems silly to me. IRL, I doubt that very many of us have put a lot of effort into learning about vampires--and since there aren't really any such things, stories can diverge more widely than stories about things that really exist can--but I think it's pretty common knowledge that a stake through the heart will kill a vampire, that sunlight kills them, and that they are supposed to recoil from garlic and crosses. That doesn't cover the full gamut of things that can be done to a vampire in D&D (immersed under running water, head cut off and mouth filled with holy wafers, etc), but it's a fair amount of knowledge. And that from people who aren't particularly studied about vampires in a world where they don't really exist.

In a world where vampires did exist, I would expect that knowledge to be at least as widely disseminated as it is in the real world not available only to the select few with knowledge: religion ranks.

The same is true of werewolves, etc. IRL, it's pretty common knowledge that you hunt werewolves with silver bullets and that they wolf out under the light of a full moon. Since there aren't any real werewolves, I would expect that it would be even more common knowledge in a D&D world. Similarly, most people know that looking at Medusa would turn you to stone even though that's a greek myth from thousands of years ago that even many of the greeks didn't believe in.

In fact, I would expect a lot of basic knowledge about monsters to be common:

Fey: Fear cold iron. Tend to use a lot of enchantment effects. Chaotic and untrustworthy.

Evil outsiders: Stories conflict--sometimes they're vulnerable to silver, sometimes to cold iron. However, Holy weapons almost always do the trick and they almost always shrug off spells like water. They walk through fire without being harmed (well, duh, they come from hell where it's always hot and flamey). Holy water hurts them too. [Confusion stems from the fact that it's somewhat difficult for a layman to tell a demon from a devil].

Undead: They fear the power of the gods and have no particularly vulnerable parts. They are untouched by many things that harm the living--poison, etc. Characters with the ability to heal probably know that their positive energy hurts the undead just like it heals the living too. And holy water burns them. Incorporeal undead would also be known to be able to walk through walls and floors, etc.

Dragons: I imagine in a D&D world, it would be common knowledge that there are lots of different kinds and that different colored ones breathe different things. Which ones breathe what would probably not be especially common knowledge (DC 10 maybe) unless there was a dragon in the neighborhood. In that case, people would know about that kind of dragon so, in Greyhawk, the inhabitants of the southern theocracy of the Pale and of northern Nyrond would know that green dragons breathe acid because they've heard stories of the Green Death who lives in the Gamboge.

Of course, if you're running some kind of non-standard D&D where there have been no unnatural monsters seen for thousands of years, some of this might not be common knowledge. Even then, however, some of it probably would be. After all, a fair amount of it is common knowledge in the real world where we don't believe in supernatural monsters either and they have never had the kind of real existence that would act as a control on the imaginations of authors.

The two big ones for me is the destruction of vampires, or lich psylactery. Are these slain enough for these to be common knowlege?

 

[TheEvil]

One of the arguments that has come up in that past against 'common' knowledge is that we live in a mass media society and D&D by and large isn't. This is very true.

However, what exactly to you think bards, minstrels and storytellers beguile their audiences with? Episodes of Days of Our Lives with gram in her youth? The tales they tell are generally about heros fighting monsters. Since every village is going to have at least one person who tells stories to while away the cold, dull winters, and since I expect that medieval people get tired of reruns too, there is going to be a good pool of general knowledge, a good chunk of which would probably be embellished, false or misunderstood by the teller. As others have pointed out though, monsters actually exist in D&D. In classical story telling and mythology, most of the things that happened were long ago or far away. In D&D, it may well have been last week near in the spooky hollow near farmer John's son's sheep pasture. You know the place. There is also the matter that adventures who hear a bard's tale may decide to correct any inaccuracies they hear. I can easily imagine a group of heros, off to slay the local monster, loading up on, say, catnip when they hear the story of how the young shepard used it to distract the beast. I can also see irate survivors 'enlightening' the bard on its true effacacy

I think most people will agree that the real problem here isn't players who have a reasonable working knowledge of D&D from play experience. It is with people who have a habit of commiting the various monster stats to memory. There is also the minor matter that there isn't a good source of disinformation for the players to assimilate the way that the characters would.

 

[robberbaron]

I agree with Adventurers having SOME ideas about "common" monsters and use Knowledge skills to gain extra information.

Don't be afraid to rule against your players if you think you position is the correct one.
If you really think that they would not have a piece of information about a monster, then tell them so.
Don't argue, just tell them that it is your opinion, backed up with your reasoning.
Reasonable players will understand. They might not like it, but they will understand.

IMO giving in to players all the time is the Road to Hell tm.

 

[PrinceZane]

Greetings,
Thanks for all the attention to the post. Sorry took so long for me to get back.

I understand that there is information that they're gonna know through stories, bardic epics, and whatnot. The main issue was how to determine if it's something the character learned, or if it's something the player knows b/c he's read the MM one too many times. Just seem to have a problem sorting between "did he do that b/c his char knew, or b/c he knew what the mob was capable through reading" *shrugs*

 

[Elder-Basilisk]

Actually, I'd say there are quite a few sources of questionably useful information and the more likely a player is to be intimately familiar with the 3.5 system, the more likely he is to have those bits of disinformation floating around in his head.

The really obvious ones, starting from most recent are:
D&D 3e--specific setting that you're not using. (Frex, a demon! We can't hope to bypass its DR without sarishan steel when playing in the Realms or, perhaps more likely "we'd better get a holy weapon or we can't touch it" when playing a character with a sarishan steel greatsword in Arcanis)
D&D 3e, Neverwinter Nights version
D&D 3e monster manual
AD&D 2e Baldur's Gate version
AD&D 2e house rules from an old campaign
AD&D 2e add-on books
AD&D 2e monstrous compendium
AD&D Monster Manual
OD&D stuff
Way before my time stuff

Tangential information can sometimes creep in from other systems too:
Rolemaster
Gurps
etc.

There's also just plain being mixed up. If your DM describes the foe to you, it can be easy to confuse, say a succubus blackguard with an Erynies fighter. Better hope you weren't counting on electricity to bypass the "erynies" energy resistance. In short, it doesn't help to know that demons generally have energy resistance to most everything and that devils are immune to fire and have resistance to everything else EXCEPT electricity if you don't know whether you're fighting a demon or a devil.

Furthermore, it's fairly easy to become confused about your various rules of thumb or to apply them. For instance, bebeliths are demons, but don't have any SR or energy resistances. But, since you know that they're demons, it's easy to assume that they do. Or, similarly, my rule of thumb for DR is: weak demons=cold iron or good, moderate demons=good, strong demons=cold iron AND good. But is a Hezrou a strong demon or a moderate one? Similarly, off the top of my head, I couldn't say whether the Gelugon is the top tier moderate devil (DR 10/good) or the bottom tier strong devil (DR 15/good and silver).

And all that is still, as they say, easy to forget at the table. I write a fair amount of D&D stuff (mostly RPGA, but I've got a credit on Goodman's Games Wizard strategy guide now) and have DMed quite a bit, so I unavoidbly know a lot of stuff about monsters. If I didn't, I'd be forgetting to apply DR when my PCs applied the beats to my monsters. But, in a recent game, I completely forgot that devils were immune to fire and blasted a group of them with an empowered fireball. Perfect execution (airburst over their heads, including the relevant portions of the wall of ice and (iirc) all three of the bone devils, but missing the PCs right next to them (and not taking much time at the table either--"I cast fireball, centered here") but it was mostly wasted because they were immune. And there I was, thinking, "it's only Fire Resistance 10." After that, I stopped being lazy and had my PC make a knowledge check to be sure about all that stuff. So our memories are another potential source of disinformation--even good memories.

I think most people will agree that the real problem here isn't players who have a reasonable working knowledge of D&D from play experience. It is with people who have a habit of commiting the various monster stats to memory. There is also the minor matter that there isn't a good source of disinformation for the players to assimilate the way that the characters would.