I've had this character for a while, originally he was written for a superhero-related story I wrote with a few friends. I've changed his backstory, motivations and his abilities to adapt to the universe the character is in now. My fantasy universe, in which the likes of Elves, humans, Dwarves, Ravens and other species co-exist in the 21st century and try to combat the threat of supernatural beings, most notably a new threat that's arising. Fred Pierce is an elemental mage, specializing in fire magic and lightning magic. While at university, he was sought out by an ancient order of Vampire hunters (still haven't come up with a name yet) who's intentions are to make sure that Vampires (and other supernatural beings) never become a threat again. They trained him to hunt and kill supernatural beings, harnessing his magical abilities. He went freelance and became a mercenary due to a falling out with the figureheads of the order. However, Fred continues to work for the order. If the people that hire him are engaged in supernatural-related activities or illegal forms of magic (i.e necromancy) he reports them, or takes them out. Fred has a lot of pent-up aggression although he tries his best to keep a cool head. He's cocky and at times quite arrogant, but hides this trying to portray the image of a "cool and confident type". As the story progresses, he begins to open up to several other characters though. The idea I have at the moment for introducing this character is the order and the world are thrown into turmoil (already an established plot-point in the second act) causing them to call in all the help they can get. The following three to six chapters would be about gaining that help introducing three (or four) side-characters, two (or three) of which have already been mentioned and/or seen in another part of the story. The other possible idea is that many members of the order have been killed or have turned against their fellow members (connecting to the world being in turmoil), prompting the loyal few that are left to seek out new members. I know a mercenary isn't very trustworthy, but they won't have a lot of choice in the story. They'd probably end up offering him money. The question is of course, where should Fred be when the other characters are searching for him? On a job or being hunted down by rogue members and/or Vampires (I might not go the route of rogue members as it seems too cliché').
In self-imposed retirement is a bit cliché but still works. In a drugged stupor that makes him oblivious, again a common trope that works. Off in the wilderness enjoying life and ignoring the world, I like that one.
I take it you are introducing him, at least in his absence, in the first chapter? I'm no expert, but I hear that's a cardinal rule of fiction writing. However you explain why everyone has to go to so much trouble to find the guy, it might be a nice (and humorous) touch to have him show up at the end of the first chapter on his own initiative, saying something like, "All right, here I am. What's this all about?"
Could you make it dependent on his motivation for hunting vampires in the first place? He must have had some reason to leave the relative security and comfort of the university to go off to train as a hunter. If he did so out of juvenile heroism, it'd be plausible for him to have retreated to enjoy life and impress the girls with the tales. If he was going for revenge, he might rather still be out and about, maybe stumbling into a less experienced character (if there is such a person in your setting) saving them from harm and can be led to reunite with the order coincidentally, or sought out knowing his rough location. Or instead of being sought actively, the order might be going after a special object that is also on Fred's own agenda, forcing him to reunite with the order and to overcome at least part of the reservations that caused him to leave in the first place. Just a few random ideas.
