I do several things to keep the player characters interested and invested in each other.
- At the start of the game, I insist that players coordinate backgrounds (subject to my approval) such that each character know at least one, and preferably two or more, of the other characters. In general, I prefer these connections be positive; the most negative I will usually tolerate is on the order of a friendly rivalry. In general, I also prefer that if you start from any one character, you can get to any other character by following these pre-arranged links. (In graph theory language, the players are all connected, although indirect connections are fine; the alternative would be two more more sub-groups connected internally but not to each other.) And finally, I try to ensure that each connection is more than trivial, but not necessarily life-binding.
So for instance, "We met in a bar twenty years ago and never saw each other again," is trivial. "We are cousins who are best friends and we are rarely separated," is life-binding and more than I look for (although it's fine if that's what they want.) Things like the following are what I look for, and/or what I've seen in the past:
- Our characters served in the same unit years ago, and knew each other, but haven't kept in contact...
- I served as a mercenary escort once, while he was travelling with his master from here to there; along the way, this happened....
- We weathered the siege/plague/earthquake of wherever together some time back....
Now, some players are genuinely not wired that way-- if you ask them for backstory, they freeze; if you given the one, they can't connect to it. When I run into a player like that, I have to respect that, but I try very hard to get everyone to adhere to the guidelines.
That does not directly solve the problem. (It actually solves the problem of getting the characters all on the same page at the start of the game.) But it does often give me enough to work with to do the following:
- With enough insight into character backgrounds, and with overlapping backgrounds, I try to give every character an mid-term to long-term goal or plot arc, and then I try to modulate that by giving at least one other character a minor to moderate interest in how the first character's arc plays out.
It's important (to me, for the games I want to run) that these arcs not be strictly opposing: If one character has sworn blood-vengeance on an NPC, I won't give another character the goal of keeping that NPC alive. But I might give another character the goal of getting something from that NPC before his death, or getting the NPC to do something, etc.
And I also try to modulate this in another direction by giving other characters-- ideally, not the same one-- influence over the plot lines. So continuing that thought:
- Player A has sworn to kill Sir Odious, his parents' killer
- Sir Odious has information that will help Player B in her quest to do something else
- Player C knows someone who can be bribed into giving up information about where Sir Odious will be
In that way, for each of the various player sub-quests going on, at least one or two others will be involved somehow, even if only at the periphery. Ideally, Player B has some motivation for something to happen, and Player C has something he needs-- something at least moderately costly or risky. They are invested.
One thing I would not do-- at least not again-- is what you tried:
I've had players create characters (with backgrounds) completely secretly from each other with the hopes of allowing the character interaction to be heavily role-played at the table. Didn't work because of very incompatible characters.
I've never done that, specifically, but I've inadvertently done similar things and it never worked well. It seems like it should work, especially if you pattern it similar to what I've outlined above, but there's a structural weakness to it: If the players, starting out with the relative blindness of only knowing their little part of the background, they just might not see those connections you built in for them, and won't give themselves the incentive to start sharing information. And if your players were the sort that would do that naturally, you wouldn't have to go through these acrobatics in the first place.
Background:I'm currently running a 5e campaign with a large number of possible NPC companions and have run Out of the Abyss (which is HEAVY on NPC companions).
Combat
The conclusion I've come to for combat is: The Companion System.
Yes, it's not part of official rules, and isn't free, but it has worked excellently.
RAW Out of the Abyss has each and every NPC use the stat block of the appropriate monster. At the beginning, there are around a dozen of these NPCs. Once I whittled it down to three, it was a bit more manageable, but still meant that I was playing a disproportionate number of rounds in combat. It felt like I was, if you'll pardon me saying so, just playing with myself. The use of multiattack from two of the characters was especially unbalanced.
I have since switched to using the Companion System from the link above. I won't go into too much detail, because the person who created it deserves your money and clicks, but it gives companion NPCs small, supporting abilities to use in combat, and puts control of them into the players' hands. Any player can choose to control an NPC at any time, as long as they aren't already "claimed".
Currently, as an example, I have a drow cleric accompanying the party. The drow can do one thing: cast Spiritual weapon, and use it. This adds a bit of damage to the 3-person party without being especially interesting, and one of the players will still get "credit" for any badassery enacted during combat. It also means one less thing for me to keep track of, which is wonderful.
Talking to yourself
As far as RP goes, I try to involve my players whenever possible. Sometimes, as odd as it is it to me (and, it seems, to you too) they actually enjoy watching the DM talk to themselves. However, in these situations, I try to paraphrase information, and then either have an NPC address a player directly, or drop hints that the party should get involved.
For example:
DM: "You come across two women in the street. They are arguing.
[doing the voice of Woman 1] This other woman has stolen my wares!
[doing the voice of Woman 2] I haven't! She's a liar!
They carry on like this for a while, arguing loudly. It looks like they might come to blows if nobody stops them."
Eventually, if your players are roleplay inclined, they'll get involved in a situation.
As for interactions with NPCs that are already part of the party, I use two strategies: the first is always asking during down time if anyone wants to talk; the second is narrating what the NPCs are doing. Often times, the response to strategy one is a resounding silence. But I like to make that space so that players don't feel like they'd be interrupting anything if they wanted to talk. As for the second option, while running OotA, making camp and resting was a common thing. I would often narrate things like:
As you settle down for the night, you can see that Eldeth is leaning against a wall and studying her battleaxe with a stony frown on her face. Jimjar seems to be practicing card tricks and looking around at everyone from time to time. Sarith is curled up with his chin resting on his knees, clutching at his head.
This helps to build atmosphere, of course, but also suggests that everyone involved has something that might be a dialogue hook; the first person is unhappy about something, the second is trying to show off and get attention, and the third seems to have a nasty headache. Now, for the record, I've never had a player whose introduction to RPGs in general wasn't through Bioware, so they all understand the idea that you should be checking up on your companions pretty regularly.
What do NPCs know?
This may sound glib, but NPCs know what they should know. The aforementioned cleric is familiar with their home temple, but not so much with the surrounding city, and certainly not the rest of the continent. The well-traveled retired adventurer, however, knows a little about everything, although it may be a little out of date. Consider the NPC's backstory first, and then decide what knowledge and skills they have.
As for bailing the party out, I count NPCs as just another tool in my box for unsticking a party. If they've gotten hung up on something long enough that they're clearly bored, I give them a little nudge. I treat these along the same lines as what I would do with any non-party NPC, and again, try to keep in mind what the NPC's skills and background are. When trying to infiltrate a temple, the drow cleric may suggest going in through a secret passage nobody else knows of, whereas a druid might suggest using their spells to bust in. This is a fiddly DM call sort of situation, and requires a good read of your players to know when they're no longer having fun beating their heads against the wall.
Final Notes
Not all companions are created equal. In order to avoid overshadowing or overpowering the party, most potential companions are at the slightly-underpowered level that the Companion System offers. Some are less useful, and might need some training and protection; some are more useful, and might be able to offer training.
Overall, my advice could be boiled down to:
- Use the Companion System, because it will save your life.
- Make your NPC party members integrated parts of the world, and let that inform their dialogue.
Best Answer
A few options for introducing the cultist:
Once introduced, establish trust. Have the cultist offer a useful tidbit of information, or speak up for the party in difficult circumstances. Perhaps have the cultist be the subject of a rescue from forces the PC's deem villainous. Essentially, put the cultist on the opposite side to known enemies. Then, when he tries to persuade them of what's going on, they'll have a reason to at least hear him out.