It's likely we have all run into trouble when it comes to plotting with others and trying to find a core conflict that can affect both characters interactively. Sometimes the conflict is obvious between two characters, but when it isn't, it can be a little tricky to start off well after that first introduction occurs in roleplay. Especially when characters are vastly different in background or theme, finding the common ground to stick them together for a long-term story is important.
Below is a list of prompts and ideas that can make the conversation easier, and potentially engage both parties in a thread. I've found that I use these five pretty regularly in some way shape or form to get ideas going.
1.) What is something your character wouldn't want to happen?
I mean the worst things they worry about. Make a list and dig deep into what their future worries are.
-What will ultimately get in your character's way and force them to change their normal course?
-What would come next after their worry comes true?
-How does that action intertwine with the other character?
2.)What does your character do normally that could go all wrong?
Focus on a task or physical thing that your character does. Make cause and effect their worst enemy.
-Have a spell misfire and hit something it shouldn't.
-Have the 'mercenary' character miss their kill. What happens because of it?
-Play with the butterfly effect.
3.) Make your character lose something important.
A thread based on finding something out means you can take your character anywhere. The situation is already abnormal enough to be put in a unique setting, and your character's searching could be interrupted at any time by another character. Finish it off by making sure the other character will have enough motivation to stick around.
-Do they want to help the cause?
-Are they also searching for the item?
-Do they have their own secret motive?
-Do they get stuck helping?
4.) Create an NPC. Make them opposites and give them a reason to dislike one another.
Put your misunderstood villains here, and there is a multitude of ways to do it. The main point here is that a story doesn't always have to be 1 on 1 alone. NPC's, especially re-occurring ones, can help you build out the world you're writing in and diversify what can happen.
-Think of who they could be chasing.
-Who is chasing after them?
-Who are they trying to avoid?
-What motivation do they have against this person?
-Are they trying to take something or vice versa?
-Are they family?
Give this NPC their own goals and reasons while you're at it.
5.) What does your character rely heavily on?
Take it away from them, or have the other character fill the void. Make the character you are writing with be their new solution to it. This leans into finding a symbiotic relationship with the other character (Just... don't lean too heavy so the other writer is doing the work).
-How would the two serve each other for the better if they stick together?
-Does it affect the other character in a good way or bad?
-How might that help them on their journey?
This also leans on the side of writing ships and relationships, but you might not be successful with just this conflict alone. That brings me to my final (and fairly obvious) note.
Now go combine them with each other.
Add an NPC that steals something from you.
Use a mishap as a reason the other character loses something. Now you owe it to them to help find it.
Let your character get lost and they're searching with who they were traveling with before.
I'm telling you what you already know, though. Few conflicts are just a single pinch point where one thing goes wrong. Layer them and add varying levels of conflict for the best results. Complexity is key to keeping one another engaged and keeping the questions coming for what will come next. Most novels have several minor conflicts that happen before the endgame, roleplay is no different.
Happy writing and I hope it makes sense. If anyone has something to add feel free to toss it in the comments.
(Here's my disclaimer that I'm not an expert and just a person) ----> x