I’ve started playing Tomb of Annihilation (ToA) with my kids. We’re just starting the adventure, but one thing I’ve noticed is it introduces GM NPCs as part of the group. Because it’s only my two sons playing (one is a rogue and the other is a monk), I often use NPCs to help the party. They’re normally extra healing of some sort (amazing how there always happens to be a friendly cleric around).
Reading through ToA, I’m struck by the fact that it almost requires a GM NPC. In this case, someone that accompanies the party and plays a role in how they accomplish the overall mission (Spoiler Alert?). Because I have only two players, this isn’t a big deal, and another character is often helpful. But if I ran this adventure for another group that has characters to fit all the normal roles of a party, I think it could take away part of the fun for the party.
Here are my guidelines for using a GM PC:
Options. Only provide options to the PCs. This is their story, they make the choices. For example, your guide says that taking the river is faster, but you must navigate the rapids.
Combat. Unless the NPC was hired specifically for combat, I normally have them go last in initiative order (like townsfolk or other extras). All rolls for the NPC in combat are made by the players. They decide on tactics with DM veto.
Spells. Rituals, buffs and other non-combat damage spells are preferred. Initiative is left to the party for specific combat/damage focused spells. Rituals – seems like they are made for NPCs.
Skills. Absolutely fair to to let the party hire NPCs for specific skills. Of course, some local governments may outlaw or restrict certain skills – but that just adds to the fun.
Ownership. Not slavery, but who directs the NPC. I prefer to get direction fro the players and then interpret. This requires your NPC to have motivation and a plan. I know this isn’t always easy (and can contradict some of the statements above), but providing a person that the party interacts with instead of just an automaton means a better experience for everyone.
If you want the party to have more healing, give them potions. If you want them to interact with a “person that can also heal them” give them a cleric with motivation and their own personality.