What might cause a lawful person to become chaotic? (D&D) Character motivation help.

[Scarlet-Devil]

I want to play an ex-monk (probably Passive Way)/warlock (CG) for an upcoming game, but I'm having a really hard time coming up with a reason for her to change class and alignment. My DM tends to require better thought-out backstories and motivations the more complex and seemingly unlikely the character is.

I think she's going to be an aasimar or lesser aasimar, if that helps at all.

Vague thoughts on backstory:
-Grew up in large, famous, but secluded monastery, receiving special attention due to celestial nature.
-Having grown up in monastery, is well versed in scholarly, athletic, and esoteric martial pursuits.
-Whatever event initially led to her leaving said monastery also related to the appearance of her warlock powers. Possibly involving destruction of the monastery, conference with an otherworldly being, or simply the sudden discovery of her mysterious abilities and the desire to practice them (perhaps she had to leave because that kind of magic was forbidden)...

[DeathsHands]

Perhaps destruction of the monastery spurred the thought that passiveness (lawfulness) leads to destruction?

[Stormageddon]

Signing a pack with a demon to attain warlock powers might enough to turn someone choatic.

[dps]

You have a character who was brought up in a very sheltered environment, and was raised in a lawful manner. A lawful alignment would have been something of a default for the character. But then, contact with the outside world could have shown the character that behaving in a lawful manner didn't always work out well (note that it might not be lawful behavior per se that caused the problems, but the particular lawful code the character followed, and the character didn't have the experience to separate the concept of lawfulness from that code). That might have been enough of a psychological shock to cause her to feel that she had to make a choice between being lawful or advancing the cause of good, and decided that it was better to be be good. As DeathHands suggests, the destruction of the monastary could certainly work for that, but there are other possibilities.

[Pisha]

Basically, anything where the laws/rules conflict with what the character truly believes is right could potentially cause some disillusionment in regards to Law.

Being forbidden to practice magic might do it. Other options might include: being forbidden to go to the defense of a helpless town right across the border (because they're out of your jurisdiction, or because your countries restrict travel); being ordered by someone higher in the ranks to perform some evil (or just unsavory) action; having the monastery destroyed because of adherence to an impractical rule (the first day of the month is to be spent in silent prayer and meditation. No speaking and no violence allowed - even if you're being invaded and it would be REALLY helpful to punch someone, or at least shout a warning!)

Actually, that's not a bad one... on a Day of Silence, the monk breaks silence to shout that they're being attacked. The monastery mobilizes and fights off the attackers, but instead of being lauded as a hero, the monk is exiled for violating the sanctity of the Day of Silence. Hmm...

Note, though, that even something like that is more likely to turn him neutral than chaotic. That takes time, and would probably be a less dramatic change. It could come about when, kicked out of his structured home, he's forced to experience true freedom for the first time in his life, and after some initial qualms, he eventually realizes he enjoys living a life free of rules. No big drastic revelation, just slow growth into a different sort of person, who can look back on his younger monastery-bound self and just smile, knowing that he would no longer enjoy a life like that even if it were an option.

[Hyudra]

It's a hard question to answer, because opinions of what constitutes 'lawful' varies from person to person. It's never really established well, and remains fairly inconsistent.

So with that said, I feel it's important to outline my own perspective: As Good & Evil alignments reflect good & evil behaviors, the same goes for Law & Chaos. To be more specific, law implies a kind of social responsibility (not necessarily to the laws of the land, though), duty, premeditated action, routine and steadfastness. Lawful societies are traditional and ordered, where things are done in a certain way and everything has its place.

Chaos reflects a flouting of convention, creativity, impulse, change and exploration. Chaotic societies are freewheeling and constantly evolving, with members of that society each doing what they see as needing to be done (or just doing what appeals to them). The people define the local culture rather than vice versa.

So with this in mind, I think there's a few possibilities:
The Monk is trained in rigorous kata, or sets of moves. But as some people will point out as you take a martial arts class, a 10th dan black belt can get the crap beaten out of him in a real knock-down drag-out fight. Perhaps the monk lost one too many fights. His confidence in the katas is shaken, and as the days go by, he finds that he's less and less motivated to wake at sunrise and spend an hour practicing his steps, punches and kicks. Rather, he's falling back on what he's learning in real fights, spur of the moment and impulsive actions. Before long, the decade of training routines and exercises are behind him and he's adopted a more dynamic outlook to reflect the dynamic world around him.
The Monk's temple held to a code or philosophy, which was said to be a reflection of the greater fabric of the universe. Part of this code included taboos or the like - things that were forbidden. Perhaps the Monk had to always sit facing North, or had to always have a red piece of clothing on his person, or could only eat things that grew above (or only below) the ground level. In the course of adventures, however, adhering to these taboos was impossible, so the Monk was forced to break them. With each one broken, the Monk's faith in the code was shaken and he came to abandon the philosophy.

[mangosta71]

Maybe the character's belief in the code she was taught is so strong that she disdains the laws of the land she travels through, leading her behavior to become more chaotic (as judged by society) while she still thinks of herself as lawful.

[Edan]

I don't have a specific suggestion but a rather broad one. Just manufacture some kind of Cognitive Dissonance (http://en.wikipedia.org/wiki/Cognitive_dissonance) for your character. Any kind of perception shattering event should do as long as it sets up horrible contradictions in your characters mind.

For example your monk might have been taught that obedience to the monastery is above life itself. Now bring in some kind of event to simultaneously exist and contradict all your character ever knew. Perhaps he sees his abbot violating the code of obedience and gets crushed by the hypocrisy. Or perhaps he is held to a double standard among his peers. When his mind breaks (cue mental breakdown) perhaps that is when his warlock powers could manifest as he suffers internally.

Just some thoughts. I think the specifics of the above posters are great.