How much should they know?

[Sunseeker]

When it comes to running and playing games, I've always struggled with how much the players should be told, and how much the players should tell me.

If I tell them that a thick cloud of greenish fog lies before them, should I necessarily tell them that it will do 1d4 damage if they enter/remain in it?

Likewise, if a player has an ability which has an effect that say, damaged everything adjacent to it each round, should the NPCs know that?

From a first-person perspective, it's unlikely that all enemies are going to connect the big firey halo around Joe with the fact that they're getting burned every time they attack him up close.

This has generally been how I run things, some NPCs ignore marks, ignore detrimental zones and effects, while some don't. Sometimes this depends on what kind of enemies are on the board. Zombies will ignore marks while Bandits will sometimes ignore and sometimes not, while dragons are smart enough to figure these things out.

Sometimes, it's a bit of the honor system, if my players are going "but wait!" a lot, they're going to find more surprises in the green fog than when they're up front, and naturally if I'm(or the DM) monster-meta-gaming around their powers all the time, they're going to tell me less about what their powers are going to do.

So what about the rest of you? When DMing do you expect to be informed beforehand? Do you inform players beforehand? Where's your "middle ground"?

 

[Mengu]

I tell them most things, and my monsters know about most things.

I know this is vague, but I like the players to know what their options are, and I like to play monsters in a manner that will provide a good tactical challenge for the players.

Whether monsters ignore marks or not is often a tactical choice, and they frequently do. But they always know that they are marked.

The few things players might not know is what happens if they enter that yellow-green cloud on the left bank of the river. They could make a knowledge check to try and figure it out. But if the fight takes them there before then, they'll figure it out the hard way.

I even try to describe monster auras as best I can. I might say, "Looks like that fire elemental is really hot, if you start your turn next to it you might take some damage," then I turn to the tiefling and say "it doesn't feel that warm to you though, it's quite tolerable." I even let them know of leader auras, "The largest hobgoblin is shouting commands right and left, and his allies close to him seem to fight more accurately than the hobgoblins you've fought before, due to his coordinated orders."

So combat is mostly open book. This isn't to say there aren't plenty of surprises still, in the form of monster immediate actions, opportunity actions, free actions, etc. And there are always mysterious terrain pieces that can be beneficial or harmful, but that can be discovered via skill checks or trial and error.

 

[AbdulAlhazred]

As far as what monsters do the Knowledge Check rule pretty well covers that. Depending on what the PC rolls they will know more or less specific information. With a high enough check a PC could be aware of most of the details of what a given monster does. OTOH they might not even have a clue what they're facing at all. How you describe that is really a matter of style. I tend to give a fairly narrative description, like what Mengu outlined. However I may provide some mechanical details if it helps the players understand what is happening. For most monsters it is pretty obvious, but there are some exceptions.

As far as effects go, the general rule is every creature is aware of the mechanical implications of any condition or effect placed on it by a power. I'd also pretty well assume most monsters understand things like marks. That doesn't mean they have the sense to react in a tactically appropriate manner or that even if they do that they pick the most tactically sound strategy. Monsters get role played just like PCs do. I'd expect the players to generally do the same, but of course since winning fights is usually pretty high on most character's list of priorities they can generally just use good sensible tactics.

As far as things like terrain or other kinds of things like say a zone I'd again fall back on knowledge. A wizard can use Arcana to figure out what a zone does for instance (again this is covered in the skill rules). If it is something more mundane then Nature, or Dungeoneering is likely to provide a possible answer, though if the adventure is say set in the Elemental Chaos then some other skill might be appropriate (probably Arcana again).