I read this exercise- a short one, a simple one- in "How to Write The Breakout Novel," and it's brilliant. It's just brilliant. Two steps. You've got your character- protagonist, love interest, villain- you've got them kind of figured out. You know their general role in the story, their basic modus operandi. Step One: What would they never, ever, do? This isn't something major in the geopolitical sense. Most people wouldn't commit genocide, most people wouldn't murder their loved one. Pick something deep and necessary to the character. What would they, personally, never do? Step Two: When would they do it? Put the character in the vise of extreme circumstances. Figure out that situation where their one most holy "Thou Shalt Not" is violated. Feel their emotional torment, their horror looking back on what they've done, the rage or terror or pain that forced them to do this. And putting a gun to their head isn't enough. Physically forcing the character to do the action isn't enough. They have to choose to do it. They have to do it of their own free will, even though better options may well be available. Example: Main character, a goblin chief from a small, weak clan on the outskirts of a small human town. Part One: It's a fundamental part of Goblin Law that goblins never harm other goblins. It's so fundamental to their way of life that the very concept of murder is alien to them- killing other sapients, sure. Killing animals, fine. But turn a blade against another goblin? No. Never. Not in a million years. Part Two: One goblin from the clan, enraged at the senseless murder of his scouting party by citizens of that town, has begun to attack the town, murdering its citizens by night, staying within its borders, not returning to the clan. In response, the humans begin to search for the clan's secret grounds, and messengers are sent to other towns. The goblin and human worlds are on the brink of all out war. The chief enters the town to find the renegade, hunts him down and tells him to return. The renegade tells him he won't. He can't. He likes killing; he has been consumed by revenge and no longer feels fear. If he returns home he'll just find more humans to kill. It will only be a matter of time. The chief cannot afford to let him live. He could. He could walk away, let the war start. But the stakes are too high. And so, the chief damns his own soul and kills the renegade. What do you think? Of the exercise, I mean.