First of all, I recognize this is absolutely a world's smallest violin issue. I should be overjoyed to have a "problem" like everyone's characters getting along. But let me explain.

I have a party of INCREDIBLE role-players. They really buy in 100% to their characters' headspace, voice, story, and to the plot itself. They come to me unprompted, one on one, to talk to me about their character's narrative and personal growth, and judging from the amount of thought and passion they pour in, they are clearly loving the game and the experience of playing their characters.

However, I've noticed a weird amount of "dead air" ingame where nobody wants to speak for fear of imposing. Everyone's characters tiptoes politely around each other. If something is happening, everyone goes along with it. There's a lot of conversations that go like: "I think it would be best to go to the temple." "Sounds good to me!" "[Character Name 1] is unsure about this, but she wouldn't say anything. She'd just follow everyone else." "[Character Name 2] would probably notice [CN1] seems uncomfortable, but he wouldn't want to pry."

It drives me wild. These players clearly love their characters and want to share. I wanna see them get mad at each other! That kind of conflict would really add some necessary heat to the story. I'd love to see it.

My absolute first thought would be to take advantage of the fact that two of the party members have sentient weapons that repeatedly attempt to possess them (these two characters are members of the same fiend-hunting organization, hence both having the same weapon). I also have a Great Old One warlock in my roster whose aberrant patron I'd like to use to my advantage. Aside from these things, do you all have any advice for shaking up a party and stirring the pot a little bit?

A disclaimer: Interparty conflict came up as a "yes please" during Boundaries discussion in Session Zero, so I know this is something people want, but seem afraid to pursue. I'd love to facilitate this for my party.

Hmmm.  That is an unusual problem.  I think you might be onto the right track though with the weapons and patron.

One thing to be careful of is to not just try to create drama where there isn't any.  You don't want to be actually instigating fights that they don't ask for.  I think your approach will need to be pretty subtle. 

If the whole party loves each other and is happy, that's actually great!  If they are just trying to be nice to each other at their own expense though, that could eventually be unhealthy.  It might come to a dramatic explosion later.  But you do have 3 outside voices you can use right away to get them to at least think about it. 

A sentient weapon might say something like 'You didn't want to go to that temple.  Why did you say yes?  Don't you have a spine?  Maybe you're not cut out for this job after all.'

The patron might say 'You followed their advice and look where it got you.  You were almost killed.  You should ditch these guys or take charge!'

Or a nice weapon might say 'I thought they were your friend. They look sad.  Don't you care about them?'

This way you aren't forcing them to fight each other.  You are letting them fight you instead.  Which is perfect.  You are all of the antagonists in the story.  They can argue with you as the weapons or patron and not feel like they are ruining their relationships with the other PCs.  Maybe they stand up to the patron.  Or maybe it gets them to think about things and open up to their friends.  As long as you aren't forcing them into situations just to cause conflict, you can help them explore their feelings.  By letting them argue with their weapons (you) they can talk through it.  And try not to punish them for it.  Don't make the patron give them an ultimatum to choose it out or their friends for example.  Just have the patron pry a little itself.  Have it scoff at them a little, but not force their hand. 

It is hard to formulate an idea to help you without understanding the context of the campaign. One thing you must avoid is creating a scenario where a player becomes the villian working against the party, that very quickly falls apart. However, from my experience there are a few ways you can facilitate interparty conflict.

First idea is presenting a dilemma where the party must decide the lesser of two evils.

Second idea is creating a time restraint on certain side-quests or optional parts of an adventure. The party will debate what should be their main priority. An example of this is: the kingdom is about to be under siege in three days and the party must prepare for the coming battle. There are several options they can explore to prepare for this, however they do not have enough time to complete everything on offer, and there is the risk that options they persue might not even succeed (like advocating the neighbouring kingdom for aid).

Third is revealing a character secret that connects two of the characters in a negative way (but doesn't shoehorn them as a villian). An example of this is revealing that the father of one character was responsible for massacring another character's family/hometown. Or perhaps the Great Old One is revealed to be puppeteering a cruel enemy the party has been hunting.

These are some ideas I can think of without the context of the campaign.

I'd also consider having a session zero. I know that's a default answer for every party issue out there, but it's a good one. In your shoes, I'd like to remind the players that it's great to be nice to other players, but your characters also have their own opinions and concerns. Disagreements help BUILD character, not destroy it, as each character is given their own individuality. Explain what "bleeding" (where real-world and fantasy-world emotions "bleed" into the other) is and help your players learn to avoid it. Heck, I'd encourage your players to have a healthy amount of conflict between characters, which will make their characters feel so much more real. If players are aware of it, then they should react quite positively.

For example, in my campaign, I have one player that is a little bit of a murder-hobo (but not to NPCs), and another that likes to negotiate with enemies. They have agreed, out-of-character, to let the conflict and tension between their characters stay, and use it to help build a fun and interesting dynamic. The players are kind and wholesome to one-another, even though their characters frequently get in each-others' way.

In a way, this sounds like the players are innately submissive at their own expense. That's a wild assumption from me, but if that's the case, this could be an opportunity to teach your players to be willing to express their own opinions in places other than D&D. You have the power to teach your players that disagreement isn't an inherently bad thing, it's the negative ways that disagreements are often expressed that are bad.

I think you may also need to unravel the player motivations from the character motivations and how the two interact in the game.

In your example about the temple ... the character might be thinking "eh, ok, why not" while the player is thinking "I don't want to go to the temple, it will just be boring and unproductive". If the player speaks up and says that they don't want to go to the temple then it is the player saying what they want to do and not the character. When you see the player being reluctant to go the temple you seem to be thinking "Hey that player's character doesn't really want to go to the temple they should say something" and then you are trying to come up with role playing ideas like the swords or the patrons to address what is really a player issue. It generally won't work.

Most people don't like conflict and I have the impression from the very brief statements made that the players may just be going along with things because their characters would be either indifferent or agree with the idea while the player might actually want to do something else but doesn't want to try to impose their will as a player on the party.

It sounds like you might like some character vs character conflicts to develop but I am not sure you really want player vs player conflicts - which can sometimes develop out of character vs character conflicts - real player vs player conflicts tend to have a negative impact on most games.

If you want some character vs character situations to develop then they should be introduced based on plot elements depending on the individual characters and before introducing them you should consider ways out of the conflict since character vs character conflicts can end a campaign (I had two players in a campaign play characters with diametrically opposed interests in magic items - a 1e barbarian that lived to destroy magic items and a gnome illusionist/thief that was fascinated by and collected magic. The gnome mostly hid their trove of magic and interests from the barbarian which lead to some interesting character interactions. However, eventually, the party came across an artifact that the gnome couldn't give up and the barbarian couldn't do anything but destroy. This lead to a character v character conflict based on their diametrically opposite views. The barbarian was willing to kill the gnome to destroy the item. The gnome wouldn't give it up so they stole it and fled successfully. It was fun while it lasted :) ... but the character conflict had a major impact on the campaign.

So, if you want to introduce some character conflict you need to think about what motivates the characters - with folks really into role playing it is much easier since they will often have a good idea of how the character will react in a wide variety of circumstances but if you introduce conflict between the characters based on the principles that the character lives by then it can backfire so plan accordingly :)

Maybe have the patron demand something against one of the others characters backstory? The fiend demands the desecration of a temple sacred to one of the other players?

Also why not have the sentient weapons be in competition with one another? The can be part of the same organisation but always vying for position. They could play the PCs against one another to ensure they are the first to break free of the weapons confines and establish a power based before the other escapes?

I would recommend digging into their backstories and find goals which might conflict with one another, and present the plothooks for these in the game. Allow them to resolve it themselves, as they sound like an awesome set of players!

For example, if there are two of them with gods, pit the gods against one another, and have them push the characters into plots which will actively harm or help one of the gods plans, and dothe opposite for the other, just as an example off the top of my head!

Maybe go to the players and workshop things they might butt heads over. Take player 1 and player 2 aside and be like "hey I've noticed [thing in 1's backstory] clashes kind of with [2's interpretation of their alignment and morals] slightly. What if we had your characters start to butt heads over that a little bit to have inject a little drama? But only if that sounds fun for both of you players."

Don't be afraid to ask leading questions or make suggestions to your players if they seem to be struggling with a lack of material for their boundless enthusiasm for roleplay. The fact that they're already coming to you with stuff means they are thinking about their characters deeply, and should be receptive to suggestions/observations if you pitch them correctly. 

I wanna say Matt Coville has a video also about how do do party conflict the right way, but I can't remember which it is exactly, but honestly I recommend most dm's give his stuff a watch anyways

Your advice is very on target because we did have a session zero. However, I've actually been wondering if it might be fruitful for me to go back and review the notes I took during session zero with the party because it has been a year and it's easy to lose sight of that kind of thing. I could definitely also use that opportunity to talk about character bleed with them.

My husband (who is also a DM) loves Colville and binges his videos, so perhaps I will see if he knows the video you are referencing and find it for myself. Thank you.

Quote from piscinban >>

Your advice is very on target because we did have a session zero. However, I've actually been wondering if it might be fruitful for me to go back and review the notes I took during session zero with the party because it has been a year and it's easy to lose sight of that kind of thing. I could definitely also use that opportunity to talk about character bleed with them.

 It's never too late to have another "session zero" - just to clarify their original request that inter-party conflict should be allowed.

MAN! You lucky! My party is more of Smash and Grab.