Each PC follows a drive, a personal motivation giving him or her good reason to act heroically and/or curiously. Given the dangers presented by travelling around the Old World, you wouldn't leave the comfort of your home solely on an undefined whim!
By following your drive, you keep the story moving and ensure that your behaviour is in keeping with the dark fantasy genre.
You do what you do to win the respect and attention you never had from friends, family or others before now. You have the greatest respect for the success and achievements of your role model, and only hope that you can do something worthy to win their approval, admiration, or just some small piece of thanks for your efforts. You draw strength from your belief in them, and aspire to be more like them.
You do what you can to defend the weak and protect the vulnerable, specifically an individual or a subset of society - like small children, those suffering from a specific suffering, or similar. While they might be able to look after themselves, you're motivated to have their backs for them, look out for them when they're not able (you know, while they sleep or when they're already focussed on something else). They might not always appreciate the attention offered, or others might take umbrage, but your purpose is set.
You have set yourself a task to gather all the things you can (of a certain type) and through completing that collection become the greatest authority or ascend to some greater level of mastery. The path towards completion is by no means simple, as you have competition, face many obstacles, and acknowledge the possibility of life-threatening dangers. Your purpose is not a selfish one - you have a greater purpose than vanity or pure fame… or your consideration of such is secondary to the greater goal.
In your culture, family, society, or establishment those who reach a certain age or level of experience can only transcend to the next state through an act of personal sacrifice. You need to prove yourself truly worthy of that honour to which you aspire, and - perhaps in doing so - you will make it clear to doubters that you have the essence for greatness, higher achievement, or to replace your mentor. The challenge will be a tough one, replete with difficulty, danger, and many twists and turns before you can return triumphant.
You have accepted a prophecy or foreknowledge from some respected member of your family, clan or circle of trust, and seek to realise it no matter the personal cost. The prophecy might be very personal or could tie you up in the business of saving the whole world, but whatever the scope you find yourself driven to succeed and prepared to put your life on the line to do it.
You owe it to (another character), whether they realise it or not. They showed you a kindness or gave you support when you needed it most, and without them you would have gone to a much darker place. Now, you feel that you owe them an almost unfathomable debt of gratitude that you might never find the right way to repay them - no matter what they might say (assuming, again, they realise you owe them anything).
You know you have a greater purpose and that the world holds something more for you, but you have yet ti discover it. You seek out that thing that will fill the emptiness of your inner void and fulfil those indistinct visions of something more. There is always something more to achieve and if you keep following your dreams then you’re certain that you will come to some personal apotheosis and find your grail.
You just want to go home, but that isn't an option in the current climate or situation. You have memories of home that haunt your dreams and shadow your nightmares, and a yearning longing to return whatever the cost. However, some things must yet be set right before you can return - and it isn't something you can resolve in a moment.
When you think of family, you experience an overwhelming surge of emotion. Whether because of the unique achievements of your ancestors, the cumulative reputation of your family line, or some perceived cultural status - like bloodline or inherited role - family identity means everything to you. You aspire to live up to the name, reputation, honour, or status - and you seek to do that whenever the opportunity arises, though never in a way that might tarnish the dignity or standing of your line.
Friendship makes you stronger. The sense of camaraderie and common cause means you can achieve things that could not handled alone. You value the sense of family more than anything else - and the feelings, you’re certain, flow both ways. You work hard to cooperate and support your friends, without question or expectation, knowing that when the time comes you can rely on them. Maybe they’re a replacement for a family you never had, lost along the way, misplaced - whatever. To you it doesn’t matter, because now you have a new ‘family’.
Your family has money, land, or power, and you - as it happens - have an elder sibling or three. The upshot, you find yourself without purpose at home and hope to find it out in the wider world. You need to find a challenge to provide a focus for your life and show that you have the greatest potential amongst your brothers and sisters. You will write a travelogue, see the world, gather snippets of rare wisdom and make a name for yourself, on your own.
You have an instinctive desire to act for the benefit of others, to protect those who cannot protect themselves. However, you do not feel this means needing to put yourself in harms way - that’s why the likes of the Watch and the standing armies of the Old World exist. You do what you can through the means that you have available to you - through money, influence, contacts and so forth. You grease the wheels with words, gestures and favours - and, in return, find the means to feed the hungry, inform the ignorant, and offer innocents the safety they deserve.
In a former life, you did something (or many things) of which you're not proud. Indeed, you find it hard to admit to them in the cold light of day. Your livelihood pushed you to do things you might not have considered wrong at the time, or perhaps you chose to take a path toward a career that did harm to others along the way - and yet, you took not satisfaction from it in the end. Now, you're seeking to find a better place and hope you can make amends.
You have a dream, an idea... a vision, perhaps. You know that it has to be right, has to be the way forward, but those whom you respect and cherish... they need to understand. To win over those who you look up to or value as colleagues, you have to find proof, have to show them. Then they will have no choice but to believe you - and can welcome you back into the fold. You want that more than anything, which is why you're willing to push it and travel this far.
Someone has done something that you cannot find it in your heart to forgive, nor can you trust the authorities to handle it. You must exact justice yourself, with your own hand. Admittedly, others may not see your cause as one that justifies the effort, but only you have a true and clear vision of the original wrong - only you can know. However, while the word might conjure a simplicity of purpose, the act itself requires planning, forethought, and a not-so-small slice of opportunity that will take time.
The cataclysm, war, outbreak or other disaster that left you bereft and alone serves as a driving force for your existence. You feel an overwhelming sense of guilt that you’re the only one who made it out alive, and now focus all your effort on ensuring it doesn’t happen again. Yes, you struggle sometimes under the weight of guilt and angst, but you shrug off the bad dreams and despair by setting your sights on making the world a better place for those who can yet ride the devastating wave of the next disaster.
Back at home, you tried a little too hard, pushed yourself constantly to compete, to fight, to ramp up everything until your senses buzzed. You considered it a matter of simply being over-competitive, but in truth you draw pleasure and something akin to sustenance from the danger. You like the stress, the scare, the nerve-rattling threat of danger that comes from putting yourself in harms way. You thrive on the adrenaline high and always put yourself forward for the tough calls and to take point.