There is one thing that I find difficult when running adventures: deciding how NPCs will react in a particular situation. This has been always one of my weaknesses and I fear that all NPCs I portrait react always in the same way.
The other day I was reading the rules for the Pendragon RPG and I discovered the personality traits. Long story short, Pendragon has 13 pairs of traits that define the personality of each character. Each element of the pair is scored from 1 to 20 and the sum of each pair score has to be always 20. So, for example, you have the pair Valorous/Cowardly. If the character has 12 in Valorous, then his Cowardly trait is 8.
How do they work in play? Every time the character is in a situation where the pair applies and its player has a doubt on how he/she will react, he performs an opposed roll. The element of the pair with greater result wins the roll and the character reacts accordingly. I find this really great to help me decide how NPC will react. In addition, the personality traits give a chivalry feeling to the characters as they are defined in line with the expected traits a knight of the Arthurian myths should show.
I realized that this approach could also be applied to Ars Magica. Actually, a list of Personality Traits (Sins & Tempers) were defined in RoP: The Divine and The Church. In this case, the feeling provided is more in line with a medieval mindset, dominated with the idea of good and evil. The pairs include Loyalty/Pride; Calm/Wrathful; Kind/Envious; Brave/Slothful; Strong/Lustful; Wise/Greedy and Just/Avaricious. For each of those, a list of personality traits (cheerful, cunning …) is also provided.
With this information in mind, what I do now when designing a NPC is to list those pairs and decide an score. A positive score for the pair means that the character is more aligned to the positive trait (the Temper) while a negative score means the character would tend to the negative trait (the Sin). For each pair, I select also one of the personality traits as the main descriptor for the pair, that is, the personality trait the character tends to show. This does not imply he/she will not show the rest of the personality traits related to the Temper or Sin but that this is the first someone should recall when remembering the character. It also applies as an specialization, increasing the score by 1 when applicable.
During play time, when I am in doubt on how a NPC will react, I perform a personality roll with the appropriate pair. The roll is always to comply with the Temper and the score will be a bonus or penalty depending on whether it is positive or negative. If the roll is successful, the character will act in line with the Temper. Otherwise he/she will follow the Sin. Let's see how it works with an example
So what do you think?