Roleplaying NPCs
Source GM Core pg. 14
Although the PCs are the stars of the game, NPCs make the universe around the PCs vibrant. They can become a part of the campaign, sometimes for years, weaving into the story right alongside the PCs. Portray NPCs however it works best for you. Some GMs keep it simple, describing the NPCs simply by their looks or their hook (see below). Others go into more detail, using accents, mannerisms, or acting.
Because NPCs have smaller roles than PCs, imparting enough information to convey their identities while they interact with the party can be challenging. When you create an NPC, start by integrating a single “hook” into their concept: a retired space pirate, a refugee from a war in distant space, or a contemplative who constantly asks awkward questions. Each hook hints at a backstory but is easily described in a synopsis. If the NPC continues to interact with the party, you can then add to their backstory later.
NPCs from adventures and other sourcebooks often include basic information about their personality, gender, and role in the game. Important NPCs often include more in-depth roleplaying tips, personal edicts, anathemas, and more.
Because NPCs have smaller roles than PCs, imparting enough information to convey their identities while they interact with the party can be challenging. When you create an NPC, start by integrating a single “hook” into their concept: a retired space pirate, a refugee from a war in distant space, or a contemplative who constantly asks awkward questions. Each hook hints at a backstory but is easily described in a synopsis. If the NPC continues to interact with the party, you can then add to their backstory later.
NPCs from adventures and other sourcebooks often include basic information about their personality, gender, and role in the game. Important NPCs often include more in-depth roleplaying tips, personal edicts, anathemas, and more.
NPC Limitations
Source GM Core pg. 14
Always remember that the PCs have the greatest role in your story. Avoid including allied NPCs who could easily solve any problem the PCs encounter. An extremely powerful NPC should be engaged with matters beyond what the PCs are tasked with or have some limitation that necessitates the PCs' involvement. Remember that an NPC is not “your character” in the way each player has a character. Though NPCs who travel with the party can be effective and fun when handled with caution, an NPC who effectively acts as the GM's character is often called a GMPC (Game Master Player Character) and can contribute to a feeling that the players are being coerced into making certain decisions.
Betrayal
Source GM Core pg. 14
NPCs, even allies, can shift allegiances. They might betray, fail, or sell out their companions, which can make for a meaningful story event. If an NPC is being set up to betray the party in some way, lay groundwork early on so the players don't feel ambushed by the twist. If the players can look back and see a clear path to this result, it's likely they'll feel the decision makes sense in the context of the story. Try to give the NPC a “tell” or a paper trail that can be found, especially one where the players have chances to pick up on that tell with smart use of their abilities and skills.
Respecting the Character
Source GM Core pg. 14
Sometimes when creating characters, a GM can unintentionally play into themes that can be harmful or hurtful. For example, an NPC with a background of abuse, a former or current slave, or a character with disabilities requires respectful handling. This is particularly true if you, as the GM, do not have the same life experience as the NPC in question. If you want to include these themes for an NPC, you should probably bring it up with your players beforehand and set expectations. You don't need to spoil the character, but sitting down and checking in with your players can help prevent unpleasant surprises and is better than assuming. To keep the representation respectful, avoid cliches and don't use the hook as a joke. Your group's guidelines for objectionable content can also help you portray NPCs respectfully
A Proper End
Source GM Core pg. 14
An NPC's story should have a satisfying ending. The NPC might leave your story when they achieve a major goal, go on to other adventures, give up their dream, or die. The death of a beloved NPC should have weight. Make it sympathetic and powerful, and ideally have it take place “on stage” with the PCs present. Be prepared that NPC deaths might stir up strong emotions within the group, and be prepared to cut the session short or to fade to black to mitigate the full brunt of the event if necessary. An NPC's death should matter beyond the PCs' emotions or search for revenge, too—maybe the NPC's sacrifice saved a village or inspired others. Let players see that legacy carried on.