Thanks, guys!
It was a year ago this week that I was putting together the building blocks that would make up that adventure, following a Christmas break where the characters slowly came to life from piecemeal notes. Good times.
To answer your question, buddhafrog, each character had an inner conflict relating to the knights, the abbey, and/or Nerath as a whole, since they're all interrelated. From this inner conflict, each character had a secret goal that he or she wanted to accomplish within the adventure. Some of them were more dramatic than others. Also, each character had a distinct relationship with two other characters in the group--one character you trusted and one you distrusted (but the players of those characters don't necessarily know the way you feel about them--only the way they feel about you). Also, each character was tied into the knighthood in some way, or the NPCs in Siege and Madness.
My goal was to make an adventure where playing the characters became its own game and encouraged interesting role-play. I wanted to use lessons I'd learned from theater, improv, and dramatic structure to facilitate intense and interesting scenes in an RPG--way easier to do at one's own table than in a published adventure, but I gave it my best shot.
An example of one of these characters from the adventure--and perhaps the least spoilery--is Sir Nordan Gram. He's an exiled knight from Nerath who used to be impulsive and arrogant. He razed a village that refused to pay their taxes to Nerath. Rival lords, hungry for his lands, had Sir Nordan exiled to Gardmore for five years to defend the northern frontier in the Nentir Vale (like he got sent to the Wall!), leaving his wife and daughter behind. Instead of ruling over his estates in peaceful central Nerath, he's fighting evil giants and ogres, learning what it means to truly be a knight in defense of the empire. As "Siege" begins, Sir Nordan is about to end his exile and return home to see what's happened to his daughter, his wife, his lands. It's the moment he's dreamed of for five years in the north. But Gardmore has taught him something about honor, given him a chance at true heroism.
So, when very bad things happen at Gardmore, what does Sir Nordan do? The system he serves is full of corruption. It made him petty, it made his fellow lords petty. On the other hand, there is true goodness in Nerath; he's experienced it in Gardmore over the past five years, become the person he was meant to be. Then again, does he throw away his life in an impossible battle, leave his wife and daughter destitute, never knowing what happened to him? His goal in the adventure is to save the refugees of Gardmore and fight against the big bad evils in their defense. There's a kind of poetry to it--these commoners are fleeing the flames as the abbey burns around them, and Sir Nordan, who once set the flames upon them, is guiding them through, showing them the way.
Anyway, his is perhaps the simplest and most straightforward of the character goals. There are personal repercussions for him based on whether he succeeds or fails to accomplish his goal.
So... there are some things to consider when building your Gardmore prequel. Or heck, any adventure. I'm having the most fun with D&D when the characters are striving for character goals. There's a part of me that geeks out over the board game mechanics, but my happy place in the game is watching what happens when the characters are trying for things with huge personal stakes and personal repercussions. I like the way those things turn the game in unexpected directions and propel characters toward unforeseen ends. That kind of play may not be everyone's cup of tea, but it's the kind of thing I enjoy.
Good luck!
-Steve
