What does he believe? If you want anything in this world, you need to take it for yourself. If you aren't strong enough to keep it, you don't really deserve to have it. You can't depend on anyone else too much, or they'll have some power over you, and if they have some power over you, they might as well control you entirely
What is the most important thing to this character? Power. Money, knowledge, strength, they're all just kinds of power. I won't stop trying to get more power 'til I have enough to not worry about anything.
Where are they from? The Hive, Sigil
Are they part of a faction? If so, why did they join? Did they pass a test? Fill out an application form? The Fated, they have a similar view of the multiverse, and he wanted allies of some sort.
Where did your character learn their profession? Where did they get their gear? To survive in the Hive, you need to be the kind of person who stabs people in the back and takes their stuff before they do the same to you. The gear he aquired from the method mentioned above, and occasionally what he doesn't sell from a mugging.
Do you have any enemies or rivals? Mr Swire has insuted a few minor gangs from his refusal to join, and there are probably more than a few clueless berks who want revenge on the man who stole all their stuff.
Where does your character call kip? Mr Swire has a small room in the Madhouse District of the Hive, although it contains little more than a cot and he intends to leave for more hospitible climes.
What's a typical day in Sigil for him/her? Assuming he doesn't have any larger jobs going on, this is his usual routine: Wake up, commit various minor crimes *pickpocketing in the Marketplace, mug the occasional unlucky Prime, ecetera*, have a few drinks while listening for any interesting info, fall asleep.
Do they consider themselves a mercenary, an adventurer, a champion of a cause or just a working stiff? What do they do as a day job if they aren't out adventuring? If you're on the wrong side of the law, do you work independently or are you part of a gang/cell? Are you likely to take anything that comes along to earn jink or does an opportunity need to have certain hooks to get you in? (Thinly veiled GM motivation question.) "Mr Swire, ruffian, pickpocket and general rogue at your service." He does his work independently of any gang. (He used to have a partner, but he got killed). As far as motivation goes, aquiring a large amount of jink is certainly the fastest way to get more power.
Detail an NPC and their relationship to you. How did you meet? What were your first impressions? How long have you known them? Do you trust this person?
What is one memory that affects you to this day? How has it changed you? (Please answer this one, if possible.) The death of his assosiate, Mr Twem. Before that, he was generally confident in his own abilities. Now, he's more nervous, with a hunger for enough power to prevent his own future untimely death.
At the end of the day, where do you go and what do you do to unwind? He generally goes to a nearby pub and has a few drinks. Occasionally, he gets enough jink to go to a slightly classier place and indulge his more sophisticated tastes..