Use this skill to ask the local baron for assistance, to convince a band of thugs not to attack you, or to talk your way into someplace you aren't supposed to be.
Check: You can propose a trade or agreement to another creature with your words; a Diplomacy check can then persuade them that accepting it is a good idea. Either side of the deal may involve physical goods, money, services, promises, or abstract concepts like "satisfaction." The DC for the Diplomacy check is based on three factors: who the target is, the relationship between the target and the character making the check, and the risk vs. reward factor of the deal proposed.
The Target: The base DC for any Diplomacy check is equal to the 15 + level of the highest-level character in the group that you are trying to influence + the Wisdom modifier of the character in the group with the highest Wisdom. High-level characters are more committed to their views and are less likely to be swayed; high Wisdom characters are more likely to perceive the speaker's real motives and aims. By applying the highest modifiers in any group, a powerful king (for example) might gain benefit from a very wise advisor who listens in court and counsels him accordingly. For this purpose, a number of characters is only a "group" if they are committed to all following the same course of action. Either one NPC is in charge, or they agree to act by consensus. If each member is going to make up their mind on their own, roll separate Diplomacy checks against each.
The Relationship: Whether they love, hate, or have never met each other, the relationship between two people always influences any request.
-10 Intimate: Someone who with whom you have an implicit trust. Example: A lover or spouse.
-7 Friend: Someone with whom you have a regularly positive personal relationship. Example: A long-time buddy or a sibling.
-5 Ally: Someone on the same team, but with whom you have no personal relationship. Example: A cleric of the same religion or a knight serving the same king.
-2 Acquaintance (Positive): Someone you have met several times with no particularly negative experiences. Example: The blacksmith that buys your looted equipment regularly.
+0 Just Met: No relationship whatsoever. Example: A guard at a castle or a traveler on a road.
+2 Acquaintance (Negative): Someone you have met several times with no particularly positive experiences. Example: A town guard that has arrested you for drunkenness once or twice.
+5 Enemy: Someone on an opposed team, with whom you have no personal relationship. Example: A cleric of a philosophically-opposed religion or an orc bandit who is robbing you.
+7 Personal Foe: Someone with whom you have a regularly antagonistic personal relationship. Example: An evil warlord whom you are attempting to thwart, or a bounty hunter who is tracking you down for your crimes.
+10 Nemesis: Someone who has sworn to do you, personally, harm. Example: The brother of a man you murdered in cold blood.
Risk vs. Reward Judgement: The amount of personal benefit must always be weighed against the potential risks for any deal proposed. It is important to remember to consider this adjustment from the point of view of the NPC themselves and what they might value; while 10 gp might be chump change to an adventurer, it may represent several months' earnings for a poor farmer. Likewise, a heroic paladin is unlikely to be persuaded from his tenets for any amount of gold, though he might be convinced that a greater good is served by the proposed deal. When dealing with multiple people at once, always consider the benefits to the person who is in clear command, if any hierarchy exists within the group.
-10 Fantastic: The reward for accepting the deal is very worthwhile, and the risk is either acceptable or extremely unlikely. The best-case scenario is a virtual guarantee. Example: An offer to pay a lot of gold for something of no value to the subject, such as information that is not a secret.
-5 Favorable: The reward is good, and the risk is tolerable. If all goes according to plan, the deal will end up benefiting the subject. Example: A request to aid the party in battle against a weak goblin tribe in return for a cut of the money and first pick of the magic items.
+0 Even: The reward and risk are more or less even, or the deal involves neither reward nor risk. Example: A request for directions to someplace that is not a secret.
+5 Unfavorable: The reward is not enough compared to the risk involved; even if all goes according to plan, chances are it will end up badly for the subject. Example: A request to free a prisoner the subject is guarding (for which he or she will probably be fired) in return for a small amount of money.
+10 Horrible: There is no conceivable way the proposed plan could end up with the subject ahead, or the worst-case scenario is guaranteed to occur. Example: A offer to trade a bit of dirty string for a castle.
Success or Failure: If the Diplomacy check beats the DC, the subject accepts the proposal, with no changes or with minor (mostly idiosyncratic) changes. If the check fails by 5 or less, the subject does not accept the deal but may, at the DM's option, present a counter-offer that would push the deal up one place on the risk-vs.-reward list. For example, a counter-offer might make an Even deal Favorable for the subject. The character who made the Diplomacy check can simply accept the counter-offer, if they choose; no further check will be required. If the check fails by 10 or more, the Diplomacy is over; the subject will entertain no further deals, and may become hostile or take other steps to end the conversation.
Action: Making a request or proposing a deal generally requires at least 1 full minute. In many situations, this time requirement may greatly increase.
Try Again: If you alter the parameters of the deal you are proposing, you may try to convince the subject that this new deal is even better than the last one. This is essentially how people haggle. As long as you never roll 10 or less than the DC on your Diplomacy check, you can continue to offer deals.
Synergy: If you have 5 or more ranks in Bluff, you get a +2 synergy bonus to Diplomacy. No other skill provides a synergy bonus to Diplomacy.