I'm not talking about circumstance modifiers. By the PHB, circumstance modifiers to sense motive should be:
-5 the target wants to believe you
+0 the bluff is believable and doesn't ask much/entail much risk for the character
+5 the bluff is a little hard to believe
+10 the bluff is hard to believe/entails a large risk for the target
+20 The bluff is way out there--
almost impossible to believe.
According to the DMG, it is usually DC 15 to get a minor lie past a canny guard. Since most guards won't have sense motive, this would seem to assume that any attempt to sense motive vs. bluff is at some bonus--as long as the person being bluffed is naturally suspicious.
It's necessary to be quite liberal with circumstance bonusses in these cases. After all, a relatively low level bard (lvl 5) usually has +10 to bluff without any magic and very few classes have sense motive as class skills. By 10th level, the bard or rogue will probably have around +20 to that check. If DMs aren't liberal with sense motive circumstance bonusses, then NPCs will constantly catch PCs running away from murder scenes with blood on their hands only to let them go when the PC says "I'm bringing medicine to my wife and six dying children and the exertion of running gave me a nosebleed." That's a balance issue.
However, it's also important to realize that these are the DCs for the target to realize that the bluffer is lying. It doesn't mean that the NPCs will do what the characters want them to do. That would usually require a series of bluff, diplomacy, and intimidate checks.
This is clear when you think about how PCs interact with bluff checks. When an NPC successfully bluffs a PC or when a PC asks me if an NPC seems honest (sense motive check), I tell the PC "if he's lying, he's doing a good job--it sounds quite convincing." The PC doesn't have to believe it. The successful bluff merely introduces new (and possibly innaccurate) evidence to the PC's mind. For example, I was once a player in a party who had tracked down a man we believed to be responsible for a grisly series of murders in a small fantasy village. When we met him, he successfully bluffed, saying he didn't know anything about it and that we should check out another man who lived a ways off in the woods. We were suspicious, and one person thought of sending a familiar in to investigate his domicile for evidence but we couldn't see a reason to actively disbelieve him so we went on to investigate the other character and missed the big bad guy. In that case, it would have been wrong for the DM to say: he makes his bluff check, you blow your sense motives, you believe him and he gets away. Instead, he told us "he sounds honest" and our characters, though suspicious decided not to press him too hard.
An even more clear-cut example is a court case. The defendant almost always claims to be innocent or to have been under the control of magic. Does that mean that he should roll a bluff vs. the jury's sense motive and if one of the jury members blows the sense motive, the crook walks? Of course not. The criminal rolls his bluff. If he fails, the jury thinks "that guy's guilty as sin--I know he's hiding something." If he succeeds, the jury thinks, "I'm not sure--he sounds pretty sure of himself, let's hear the rest of the evidence." If there are three convincing witnesses who saw the accused pulling the trigger and he was found with a gun in his hand which matched the ballistics of the bullet that killed the victim, it'll take more than a DC 30 bluff check to convince the jury that the accused is innocent. He'll have to call other witnesses to his side, cast doubt on the veracity of the witnesses, and invent a convincing alternate explanation of the circumstances. Assuming he's really guilty, that's a series of difficult bluff checks not just one.
Bluff isn't mind control magic--it's being a good liar. In a fantasy world with potions of glibness, etc. there are a lot of good liars out there, so the logical reaction for an NPC confronted with an outrageous claim which he's on the verge of believing is to try to verify it in some way. This certainly doesn't make the skill worthless. It merely means that one needs to be careful about how one uses it.
The character who convinced the guard to go check with his superiors will get another bluff check to convince the superiors. The character who convinced the guard to check if the king was in his chambers has just eliminated one guard from any potential conflict. In general, however, it's stupid to tell high risk lies about verifiable things (unless you've made certain the verification will come out in your favor). Unless verification is really difficult or risky ("we've a radiation leak at the moment--do you want to come in and check it out?") both PCs or NPCs will usually attempt to verify the truth before taking a big risk on the word of someone they don't really know or trust. Allowing one use of the bluff skill to avoid attempts at verification is an invitation to anyone with the bluff skill to abuse the campaign world to no end.
Artoomis said:
Elder-Basilisk, you have really watered-down the Bluff skill.
What you are talking about are circumstance modifiers that should be applied. In the case of pretending to be the King, if the player provides an at least plausible story (even if it's a big stretch), and the DM gives an opposed roll, the whole bit about "I thought the King was in his chambers" provides the basis for a circumstance penalty to the PC's Bluff roll - maybe a really, really big one, maybe even enough to make it impossible.
That's the control on the Bluff skill - circumstance modifiers for really outrageous attempts - sometimes enough to make it impossible.
It is patently unfair to the players to allow a Bluff check to succeed and then tell them they are not believed anyway. In that situation, whay ptu any ranks into Bluff at all?
The Bluff skill is not to fool someone into thinking you believe something they know is false - it's about convinving them that some falsehood is the truth.
As for PCs - it's up to the DM to help them declare what they think is true. Bluff and Sense Motive checks might be used to help in that determination. Then again, if the PCs are not working together then the campaign will likley fall flat on its face anyway.
