I have this 'element' in my storyline, it basically goes like this, but there's also the rest of the game going a long with it:

Throughout the game there's this character who's being very kind and trying to make things easy as possible for you, guiding you through everything and helping you get out. Towards the end of the game, you become uncooperative, and then they turn against you and believe you should be penalized for working your way through the adventure, then refusing to cooperate. They turn into a badass monster and try to kill you, you stop them, the end.

Most of that stuff happens towards the end, but how can I make this character throughout the storyline, before the betrayal, seem like they'd never do such a thing. Which traits should I avoid when it comes to making a character seem like they'd be the unexpected to betray someone?

And when the betrayal happens, it's because you're refusing to do something (a very bad thing) that the character is telling you to do. How should this character act before and after the betrayal?

Make that character the most innocent character in your party, kind of like the lead female characters in the Final Fantasy games like Yuna.

But seriously, you know everyone is going to be aware that there's a character in your game that's going to turn on us. This is usually something you want to keep a secret until people actually play the game...lol

This is actually a tricky thing to do, I mean effectively.

Really you should be giving the betrayer chances to avoid doing something similar to what they'd do later on without going over the top about it. It would be mainly dialogue orientated, so depending on the amount of party conversation the difficulty of doing so would differ, having equal amounts of conversation from each might also be essential for not giving the game away.

That would be a key thing, leave subtle hints but nothing emphasised. If you dwell on a choice too much then it becomes obvious that either you're trying to push their personality too much or hiding something.
I don't know if it would work right but if you're having dialogue during map exploring then something like a full party talk as to their next action could bring an opportunity to make that character slightly opposed do the rest, and depending on how it's done you could have that character seem to brush it off as if it's not important. Containing themselves for later and letting issues build upon giving more reason to burst later on.

Just some general advice, I'm not sure I've looked over your project to know and understand more about it (ie the goals and characters), so I hope this helps in some way or another.

EDIT: Actually Ganstaguay this could actually work in Spaz Bunny favour, we know now that there's something to look for within the dialogue or backgrounds of the characters involved. Making it more intriguing and have more people paying close attention to the details surrounding and within the game.

If you think looking at my game style would be beneficial when it comes to giving me advice, the link is in my signature. My game actually doesn't really contain much of a 'party', but the person I want to betray the main character, is with them at all times, serving as a guide, until they go a bit too far and the main character refuses to cooperate due to the intensity of the request. If you go read about my game and possibly play the demo, it might be a little more than obvious which character I'm talking about here. But I think, as you're fellow developers, I'm not sure if I should be afraid to spoil or not spoil my game's story.

well, from a writing standpoint, i think it's always helpful to break down the emotional components within the character. pick two emotions and be as specific as possible. The first one is what drives that character to this position in the first place, and the second emotion is what you want to the character to inspire in the player. If you make those two diametrically opposite, but work to make them congruent with each other throughout and you can have a believable but still dramatic betrayal.

I haven't played your game yet, so I can't say for certain what those two emotions are, but I think if you craft the entire experience around emotion #2, and make sure they coincide with and can be driven by emotion #1, you'll do fine.

It depends on how you want the betrayal to be executed.

There's accidental betrayal, where a character is only trying to help and ends up divulging information to an unsavory source thinking it'll help.

There's ulterior motive betrayal, where a character is pushing the others towards his or her own agenda, and when they deviate that character's sense of control causes them to become hostile, irrational, and destructive, which eventually spirals into betrayal.

There's manipulative betrayal, where a character places a mask or front that the players believe up to the point where everything falls into place, at which point the character will have no use of the other pcs and throw them aside.

Those are the only 3 I can think of.

It's about motive,

M.I.C.E

money
Ideology
Compromise / coercion
Ego

pick a motive.

If you want a true betrayal, then it means you have a character that starts off with one off the above, being in line with the team. (not C)
but as time goes one that element that motivates the character is answered to elsewhere.

ir you have the "C" element move him against the team, against his will.

though in a fiction story "C" is gonna feel like a cop out.

leaving you with the others.

in terms of game lements / story.

Ideology is the obvious winner (though dont feel restricted to that!!)

a nice dynamic (especially if this guy is gonna be a boss) is to make him the most powerfull member of the team while he is on it.

example:
Jim joins the team, to fight against the evil king, because people are suffering.

he is with you because he is fighting for the people.

at a certain game point.

he is recruited by "red faction" who sway him towards communism in a tavern.
this is what will save the people.

his motive remains constant,
but his team changes, because his new team is more in line with his motives.

there is a stand off,
you've killed the king, but red faction come along to take power.
he is their champion.
there is battle.

hit point hit point.

whatever you chose to be the key driving force behind this character, have the world around him present a better option.

he works against you now for the same reasons he worked with you before.

How to make it unexpected:
-Maybe some sort of self-sacrifice. Like maybe the character steps in front of a gun to shield you. Then I guess the next part of the plot involves them gradually regaining their health or w/e. No way would that character betray you, right?
-Perhaps you entrust the character with something very valuable to do something with it, and they leave the party to go do it. Someone in your party worries that the character could just run off with it and keep it, but later the character returns and you feel silly for doubting him/her.
-Maybe the way the character originally interjects himself/herself to the party involves giving the party advice about a specific dungeon raid, and then once the party is raiding the dungeon, the character goes into the dungeon to either say "Wait, I made a mistake, go the other way," or whatever. Perhaps the character then gets hurt by a monster or something, so that you think "Oh, so I'm really aware of the dangers this character has braved to come bring me this info."
-Maybe at some point, you do something shitty to the character, whether it be steal a member of the opposite sex from them, or accidentally burn their house down, or accidentally run over their cat or something, and they completely forgive you. Absolutely no hard feelings.

Make it someone who the player cares about as well as the protagonist. A party member will definitely make it more dramatic I think

Mourn
Emotion
How, & why

MEH.

Every author has their own formula to portrait a betrayal. It really depends on not only the situation, but you as an author.

Hope this helped,

- Script

put a final fantasy 6 song, dramatism guarnteed :3

Well, i good idea is, in the finl bos fight the character reveals his true "identity" and start attacking you alied with the final boss xP

The best way to instill drama through a betrayal is making the characters featured in your game feel "alive" enough where the player can actually relate to them and will eventually begin to care about them.

This can be done with well-written dialogue and character building as the game progresses. The more "alive" your characters feel, the more the player will feel when one of them is betrayed by a dear friend.

Give each character a set of unique emotions that makes them who they are. Now, I'm not necessarily saying you have to have an optimist, a pessimist, and an in-betweenie, etc. I'm just saying each person in real life has their own emotions and mentality that makes them unique, just keep that in mind when designing your characters.

Some things that you might want to try is putting in another character that is more likely to be the person to betray.If your main character is a fine upstanding knight for instance then that other person could be rogue or a mercenary someone who's motivations are dubious at best.

You drop subtle hints of who it is .. like little things the real betrayer may say
In the end nothing is more important than loyalty
or
A man's word is the only thing he truly has.Without honor he is nothing.
Something that gives some indication of what his motivation may be but you don't do it too often just once or twice in the whole story arc is great.Other than that you make this would be betrayer so clean he squeaks.All the while presenting elements in the story that make it seem more and more likely your mercenary (or whatever) is the betrayer.ex. coming in or leaving at odd times, arriving at rendevous late, talking to strangers that leave at your approach things like that.

In the end everyone will be wondering how they could have missed it because those few occassions he gave for his motivation will come rushing back to the player.To me this is the best type of betrayal.

The main thing should be that their betrayal is due to them following that motivational factor of theirs.. be it love for the hero, or for a sense of duty or what have you.If done right you have a real face palm sense of "of course" as well as a sense of dread because well you're usually losing someone you thought of as pretty important to your party.

Well, I have a tactics RPG currently in design phase, in which betrayal is a crucial plot point: no matter what you do, one of the 37 main characters (though not always the same one) will turn against you in the end.
The motive for betrayal is perceived inferiority: throughout the game, a plot device forces characters to form pairs of 1 male and 1 female. Given that there are 37 characters (18-18 boys and girls, plus the protagonist, which is determined by the player), this won´t work out and someone will remain alone. The pairs are determined only by the player, for sentimental and gameplay purposes (e.g. team up a black mage boy with a white mage girl and after a few battes, both will learn the red mage job). The character left alone will feel inferior and his/her self-esteem will fall low because (s)he doesn´t feel loved (pairs are romantic couples BTW). When at the end of the storyline, they get the chance to obtain an artifact that can manipulate time, they go against their former comrades who try to destroy the dangerous treasure.
I intend to use this as a basis for ˝guilt-based gaming˝, as players will understand the motives of the traitor and will no doubt feel that (s)he ruined that character´s life and self-confidence, only to teach that illusionist job to some other character. Any way, since any character, including the player-named protagonist can end up as the main villain, it´s supposed to prove that anyone can be a traitor under the proper circumstances.

This is a very good question, and one that pretty much everyone here has hit the right key.

It does definitely come down to you as the author, and the story you're creating. Everything is completely up to you and you're in control. That being said, since you know how this all plays out, you need to 'set the stage' for this betrayal.

The main key is emotion.
Emotion of the characters has to fit them, their background etc.
Emotion of the player towards these characters. You have to get the player believing these people could be/are/would be based off real people regardless of the fantasy realm you're creating for them. They have to strike certain chords in a players' psyche for them to become attached to them.

Any of the versions of betrayal previously mentioned could very well be potential real scenarios in real life. Think about the times you've been betrayed in your life. Even simple, little silly things that your parents or childhood friends did that embarrassed you or drove you insane with anger. As a writer - even for a game plot - tapping into events that happened to you or those close around you are very good stepping stones into creating something realistic on paper - or in this case, in a game.

You could also use the smokescreen tactic.
Where you set up a secondary character to seem shifty, and basically distract the player from their suspicions while the true betrayer acts like they're the support for the main character. This can be difficult to do, but if you've spent the time developing all your characters, no matter how minor a role they play, this will make their actions/words more believable in game.

I would suggest that before everything think about your own best friend.

- Why is he your best friend?
- How much can you trust him?
- Would you “put your hand on fire for him”?

With that answered in your head… Here are some things I would like to include in the story to make him even more “trustful”.

1. Make him have his downsides moments and make sure the hero is there to support him when that happens.
2. Don’t make him to innocent because that can give out. Make sure he imposes himself in some situations but nothing too outrageous.
3. What makes this unique time different from the others? Why are they doing this ‘terrible’ thing to make the hero thinks it’s too much? It is not a betray if they all of the sudden change.

Well, it seems a lot of people have posted their thoughts. But really, you probably need to create the suspense throughout, leaving subtle clues, but not making it entirely obvious that one particular character will betray you or that such a character even exists. You may want to create situations where the player is blind-sided to think one particular character will behave one way, only to discover they were wrong and it's somebody else entirely, but you also don't want the betraying party to suddenly become known without some sort of hint. You want the player to think "Ahhh, I didn't see it coming, but now that I think about it, it all makes sense."

I'll give you an example. The most obvious person to act a certain way usually is not; and the least likely person usually is. Trying to find a middle ground character that could lean either way, and work on him. Give him some compassion to but a hint of a dark edge, and the player will not be sure which way he will go.

What helps is creating the feeling you can trust no one but that person. (a very unfriendly setting) That way, the betrayal will hurt double because afterwards, you have no one to turn to.

Here's my take on what you should not do. DO NOT:

-Go through the story without leaving any clues and then leave the character's defection until the very end. That's not drama. That's lazy writing.

-Shoehorn yourself into making the betrayer "the most innocent-seeming character" or some other stereotype. Your characters should be rounded and multifaceted. (That way you can make anyone you please into the betrayer.)

In the end, it comes down to how well you've written your characters. If they're flat, any kind of emotional discourse occurring between them will just be boring and pointless to the player.

I hope I was able to help in some way. Good luck!