Giving NPCs some biases and adding a simple game mechanic to deal with them adds some nuance to role-playing, negotiation, and diplomacy. Players may leverage NPC biases to gain allies when those biases align with their purposes. An NPC who is known to be a staunch critic of the church may be more easily recruited to help expose a corrupt bishop. Other times, they may need to tread carefully to win someone's cooperation, or simply to look in more fruitful directions for assistance. If they're not careful, they might even end up with an adversary. A male chauvinist might not be the best choice to help the PCs secure the ascension of the royal princess to the throne.
The thrust I'm going for is to make it easier or more difficult for PCs to gain the cooperation of NPCs according to the NPC's beliefs and values, without making the NPC's reaction a foregone conclusion or a whim of the DM. Thus, the basic mechanic is still the 2d6 reaction roll. If PCs make a request that touches on one of the NPC's biases, the NPC's reaction is modified either positively or negatively. By limiting the DM's role to deciding when to apply adjustments, the NPC's biases carry some weight, but persuading an NPC isn't wholly a matter of persuading the DM, and the DM may watch the interaction unfold rather than dictating it.
Biases come in three strengths: Ordinary, strong, and fanatical. An ordinary bias adjusts reactions by either +1 or -1 when the relevant topic is discussed. A strong bias modifies reactions in the same way, but talking about the topic is not necessary: if the PC is known or believed to be associated with the object of bias, the modifier applies regardless of the topic of conversation. A fanatical bias acts like a strong bias, but Charisma bonuses and bonuses that would apply from bribes or gifts are turned into penalties instead. To determine the strength of a bias, roll 1d6: 1-3 = ordinary, 4-5 = strong, and 6 = fanatical.
An NPC's biases may be noted succinctly in his or her stat block or description by naming the bias with a word or three and denoting its direction and intensity (e.g. with a + or a -, repeated two or three times as necessary), and easily applied to interactions.
This should stack well enough with the system outlined in my previous post regarding NPC temperaments and PC modes of persuasion. It's a few more numbers to crunch, but it doesn't seem any more complicated than combat.
John Smith, innkeeper: AC 9, hp 3, Move 40, #AT 1, Dam 1d4, Save NM, ML 7, AL N
Bias: Ruler+, Magic ---, Fred Miller ++
So, two brief lines added to the stat block, and we know that John is fairly well-disposed toward the king, hates magic to an almost pathological degree, and is fond of Fred Miller to the point of also being favorably inclined to Fred's associates. He also has a rather high opinion of himself. Easy.
This post would be woefully incomplete without a table of possible biases to roll on. I suggest giving each NPC 1d4 biases. Duplicates may be rerolled, or treated as increasing the intensity of the bias (to a maxium of fanatic, of course.) Roll any die to determine whether the bias is positive or negative: Even result, positive; odd result, negative. (Sometimes this might seem to make little sense, and you can apply some other probability, or just decide outright. An NPC who hates his own race, religion, or social class can be an interesting character, though.)
The bias table may also be used to determine general biases for groups of people, such as guilds, churches, and towns. A guild may have a bias in preference of men, a church might condemn non-clerical magic, or the population of a town might be devoted to their faith and hate foreigners.
5 Cultural or social institution
7 Guild or other organization
12 Other village or town
13 Particular person (or group of people)
15 Political faction
17 Religion, others'
18 Religion, own
Some of these are pretty straightforward, while others require some further decision and development (which is too campaign-specific for generic subtables to be of much use.) There's obviously some overlap between some of these - for instance, a bias for or against the noble house to which the current king belongs (Political Faction) might also imply a bias toward the king himself (Ruler.) Sometimes a bias in favor of something implies an opposite bias against its opposite, but not always. An elf could believe that his race is superior, without harboring any particular ill will toward others, for instance. The odds of a bias in the opposite direction generally increase with the stength of the original bias. Needless to say, use your own judgment in such cases.
Adventurers: People who seek thrills and treasure in the local dungeon. You know the type. Heroes to be admired, or murderhobos who stir up the local monsters and then disappear?
Aristocracy: The upper crust. The titled classes. Lords, ladies, and "old money." A cut above the rabble, or loathsome parasites?
Beggars: Unfortunates who deserve sympathy, or shiftless lazy drunks?
Chaos: Creativity, individuality, and freedom, or disruption and discord?
Cultural or social insitution: Long-standing traditions or lofty ideals around which societies are built - liberty, equality, the divine right of kings, slavery, war, peace, Elven supremacy, harmony with nature, patriarchy, etc. Choose one.
Foreigners: People from other lands, with different languages and traditions. Exotic and romantic, or interlopers from lesser cultures?
Guild or other organization: Any organization that is not formally part of the government, such as merchants' guilds, thieves' guilds, peasant unions, the church (the organization itself, as opposed to the religious beliefs it purports to represent), secret societies, or any other association that exists in the campaign world. Choose one.
Homeland: The NPC's native country or region. Patriot or dissident?
Law: Foundation of society, or stifling conformity?
Magic: Spells, spellcasters, and magical artifacts. Wondrous and miraculous boon or dangerous black art?
Merchants: Peddlers of prosperity or parasites on the backs of the lower classes?
Other village or town: Beloved sister community, or arch-rival? (Wullerton? Ptoo!)
Particular person (or group of people): Somebody for whom the NPC has a strong affection or an enduring grudge. Possibly a group of people, such as a family or clique.
Peasants: Salt of the earth, or grubby...peasants?
Political faction: A party, noble house, or political movement. Liberal or conservative? Royalist or anti-royalist? Lancaster or York?
Race: Either a sub-race of humanity, or a demi-human race. Choose one. Could be favoring one's own race, or scorn for others, or both.
Religion, others': Fellow travelers on a basically good path (even if it's not entirely the right one) or damned heathens?
Religion, own: Guidelines for a good life, or The One True Way...or an idiotic set of beliefs one must espouse to avoid the Inquisition?
Rulers: Kings and queens. The people who don't just make the law, they ARE the law. Benevolent and just leaders, or cruel tyrants?
Sex: Encompasses biological sex, sexual preference, and gender identity.