Preferences Make NPCs Feel More Authentic

NPCs make game worlds feel more alive by populating them with characters. But it is important to ensure NPCs feel real, not just cardboard cutouts. To evoke the impression that NPCs are actually people, your game's mechanics need to simulate preferences. Real people do not exist just to help us; they have their own needs, goals, and unique preferences and dislikes.

One of the simplest models of NPC preferences is what I call "goodwill banking," after the goodwill mechanic in Rimworld. In Rimworld, there are other factions in the world, and you have a goodwill score with each. The score rises when you do nice things like trade with them, give medical care to their members, and complete their quests, and falls when you harm them. If the score rises high enough, you can ally with them, allowing you to spend goodwill as a currency to call for help, such as requesting a trade caravan or military aid.

Having different methods of gaining goodwill depending on the NPC enhances the illusion of personhood by simulating unique preferences. In Dungeon Crawl Stone Soup, you may choose one among a large pantheon of gods to be your patron deity and gain "piety" with that god by acting according to their precepts, which you can spend to invoke various miracles. Some gods have special conditions for gaining piety; for example, Ashenzari the Shackled grants piety for using cursed equipment, whereas Zin the Law Giver gives piety for donations of gold. They may also take issue with certain actions and reduce a player's piety: Cheibriados the Contemplative dislikes it when you use abilities that make you faster, for example.

One of the strongest indicators of personality in NPCs is revenge. NPCs that want to take revenge for wrongs done by the player feel proactive and like they have a life outside the player's story. Their willingness to go after players makes them feel like more than just puppets to be pushed around. In Dungeon Crawl Stone Soup, abandoning a god results in "penance", where they periodically visit their wrath on you by summoning themed monsters, casting spells, or otherwise harming you at varying intervals.

Factionalism is another powerful source of authenticity for NPCs. In the real world, factions develop because of disagreements in values, so it makes sense that the same happens in games. If befriending one NPC or faction immediately makes you enemies with another, it reinforces ideological differences between those factions. In Emperor: Battle for Dune, players have several opportunities to ally with subhouses. If you ally with the Fremen, you cannot ally with the Sardaukar and vice versa. When there are multiple NPCs, making alliances mutually exclusive adds to the illusion that they are real by showing they have relationships with each other, independent of their relationship with the player.

When designing NPCs for your game, look for ways to give them preferences, ideally unique ones that distinguish them from each other. Your objective is to make players think about what the NPC wants, not just what they want from the NPC.