I am developing a little homebrew (mostly derivative) set of rules. The starting point is Chronica Feudalis (by Jeremy Keller), which is like FATE using polyhedral dice to rank skills and aspects, in the vein of Earthdawn, Savage Worlds, Dogs in the Vinyard, or Agon. My design goal is to come up with a unified mechanic based on descriptive phrases (aspects) that will cover everything: skills, gear, special abilities, injuries and condition, and, well, character aspects. If there is interest, I'd be happy to describe where I am so far.

What I am struggling with and would love input on, is how to represent characters as driven. Characters in this game all have a goal, a mission, an obsession or mania that propels them forward and that forces them to make narratively interesting sacrifices. They also achieve goals, or refine them, to go on to the next goal. Good stories are about heroes and heroes are people who have the will to persist until they break or the resistance before them breaks.

It's part of the setting, which is based on Alfred Bester's The Stars My Destination (originally published as Tiger! Tiger!). The book's hero, Gulliver Foyle goes from a useless unambitious lump of a man to powerful hero, because he is driven. First by the need to survive marooned in space, then driven by vengeance directed at the ship that passed him by, next by vengeance against those who commanded that ship, then those responsible, and finally against all forces that keep mankind shackled and disenfranchised. His goals grow and evolve as he learns and educates himself, but at every point of the story he is driven to steal, rape, torture, cheat, kill, and betray his friends. He comes up against the most powerful men (and a woman) who are equally driven. It's what this brilliant book is about. (The book also has the most mind bending climax in the history of science fiction, imho.) Here is a piece of dialog from The Stars My Destination:

[Y'ang-Yeovil:] "Christ, he is insane."
[Foyle:] "Am I? I've handed life and death back to the people who do the living and dying. The common man's been whipped and led long enough by driven men like us. . . . Compulsive men . . . Tiger men who can't help lashing the world before them. We're all tigers, the three of us, but who the hell are we to make decisions for the world just because we're compulsive? Let the world make its own choice between life and death. Why should we be saddled with the responsibility?"
[Y'ang-Yeovil:] "We're not saddled," Y'ang-Yeovil said quietly. "We're driven. We're forced to seize the responsibility that the average man shirks."

That's what I want to represent: characters who are forced to seize the responsibility that the average man shirks. How do I do it?

Since this is a FATE-ish game, the easiest approach is to use an aspect, that can be invoked and compelled to give a bonus or a little narrative control. But this Driven aspect needs to be an über-aspect, more powerful and pernicious than regular aspects (like "veteran of the OP war"). I have toyed with adjusting the fate point economy to achieve this, making invocations of the aspect free, and compels expensive to resist. Given the ranked dice approach to aspect I can easily represent levels of drive: from vague hope to obsessive mania. The problem is how do goals-as-aspects change as they are achieved? Another approach is to represent it as a Key from The Shadow of Yesterday. I like that idea because keys feed into character development and can be bought off once if goals are achieved or abandoned. But I want a direct mechanical effect on tests and character decisions---more than handing out experience points for play according to a key - I want to drive the characters (without railroading the players). Ultimately I'd like the players to realize that when they act according to their drive, their potential alienation deepens, and when they act against their drive they become untrue to themselves: they change who they are.

The ideal here is the powerful moment in the story in which the character must make a difficult choice between his integrity, loyalty, and dignity on the one side and goal he is driven to achieve on the other. And of course that choice will also be between him or herself and the other PCs.

Comments/thoughts very much appreciated.

Rape? By a 'hero'? And to a fair extent also, torture? By a 'hero'?

I think you can have stories about...beings...whos acts are like avalanche and it's...significant to think about. But not boys own adventure "hero's go on a romp and get called hero's at the end" stuff, though. I'm thinking of the barbarian Cnaiur from the prince of nothing series, as an example. Not to mention Kelhus from it...

But heroes? In terms of rape? Isn't it time to give up the words used by more safe media? Atleast in terms of this project?

Also I don't know if this is an issue, but it sounds like your talking about characters who will break whatever taboo or old habit - in fact, predictably so. The only real question is, as you put it, whether they will choose between themself or the PC's. The problem being if this leads to four hours of stuff, then one magnificently huge moral dilemma at the end of the session, rather than moral dilemmas spread throughout the four hours? Do driven have moral dilemmas?

I dunno if I've talked about it in a way that makes sense, there isn't alot of common phrases for this stuff.

I understand the objection to the term "hero." Foyle is despicable, and you might as well call him an anti-hero. (The book raises the question whether the vile animal Foyle in the end is more human than the civilized but cynical and brutal leaders of society.)

I am not looking for a game in which taboos get broken as a matter of course, and there is a sense of license to behave irresponsibly. But your reply points out the danger that I could get there. What I had in mind is more along the lines of sacrifice, which requires that the driven care for what they might sacrifice: a choice to give up something meaningful and precious. I am struggling with finding a mechanic that will create consequences for the characters that flow from their choices, both in terms of their power to affect others around them and of the impact choices have on the personality of the characters.

I'm kind of reading you to mean you want to have consequences and as that'll make the players care about their choice. I might be entirely off in that reading - the following is only if it is. I think observably, someone who is interested in answering the question (through a particular character) on sacrifices in general wont need consequences to care, because as said, they already care about it. Consequences are a nice addition, but are optional rather than needed.

I think someone who needs consequences to care is probably thinking in a tactical mode - ie, a gamist approach to play. Or atleast that's how consequences would strike me if I were playing - if they were going to make me care about anything, it'd be my own (as a player, not character) plan on how to navigate the game. Perhaps I'd see a relation between the actual character and consequences, but it'd be secondary and not what 'play is about'.