As a writer, sometimes you want a character to be mysterious. In good writing this mysteriousness should either further the plot, or speed along one or more of your main character’s emotional arcs. Sometimes, the character just is mysterious because that’s how she or he first came to you, the writer. Whatever the case, once introduced, a mysterious character must be handled with care.

Anyway, there hadn’t been an issue of Hulk in the rack in several months, so I had missed the previous few issues, and I didn’t know how the story line had gotten to this point, but there the Hulk was, and some strange guy in a yellow and blue costume seemed to be fighting him. Of course, I bought the issue. We didn’t learn much about this Wolverine guy in this issue. He apparently worked with the Canadian government and had been parachuted into the wilderness to try to stop the Hulk from rampaging, or something like that. Note the text in the black arrow on the cover: the world’s first and greatest Canadian super-hero!
Note that this is not an X-men comic. In 1974 the X-men were on hiatus. Their magazine was being printed, but it was reprinting stories from the 1960s, for reasons that must have made sense to an accountant, somewhere. The team had never been terribly successful before that. It would be a couple more years before the team was Re-booted (though we didn’t use that term back them), with a lot of new members and only a few of the old, and Wolverine began his off-again, on-again relationship with the X-teams.
For a long time he was a cool character precisely because he was mysterious and always seemed very reluctant to get involved with other people. It’s not exactly an original character type, but generally it worked pretty well. He’d come to help with a specific problem for reasons that weren’t always entirely clear, be gruff and business-like and morally ambiguous, betray a glimmer of affection or respect for one or two characters, then disappear for awhile, only to turn up again and repeat the process.
The problem with mysterious characters is that, if they catch the reader’s attention, the reader wants to know what’s behind the mystery. A writer may keep tantalizing and teasing readers for a while, dropping hints here and there, but you have to be careful, because there’s an extremely thin line between tantalizing and annoying to the point of wanting to take the writer by the throat and squeeze the life out of them.

You don’t want your mysterious character to turn into the Sphinx.

One problem is that the revelations have been contradictory. Subsequent attempts to make the revelations less contradictory pushed his backstory into pure ludicrousness. And his characterization has consequently become worse and worse. He’s a loner, except that he’s joined pretty much every team Marvel has ever published. And has picked and consistently abandoned a disturbing number of adolescent female protegés/sidekicks. He’s supposed to be a highly skilled assassin, except he’s a chaotic brawler. He’s supposed to be an honorable Samurai (with all the training in the ritualized combat/politics of same), except he’s also a savage killing machine. He’s amoral, except he’s noble and self-sacrificial.
Now, when a character is appearing in a series, and written over a number of years by different writers, this sort of thing might appear to be unavoidable. Except that it doesn’t have to be. Batman, for instance, has a much longer publishing and movie history (first appearance in comics in 1939, first movie in 1943 {a delightfully cheesy serial that I happen to have a copy of, if you want to watch the WWII era special effects and dumb cliffhangers}), but despite all those reboots, retellings, et cetera, the central core of the character has been kept intact: witnessing the murder of his parents as a child, he obsessively trains and studies, eventually becoming a dark detective and vigilante who prowls Gotham at night, foiling criminals and bringing the worst to justice. At various points they’ve wandered into the quite campy, to the darkly romantic, and other odd places, but all of the writers have managed to bring the character back to that core.
I’m working with a mysterious character in my current novel in progress. The previous novel, to which this is a sequel, also had a mysterious character—one of my two protagonists. But she wasn’t a dark, brooding person with hints of a tragic past. She’s one of the most cheerful and optimistic characters in the whole book. There were simply mysteries about her from the beginning, hints were dropped here and there, until during the big battle at the end (it’s a light fantasy with epic fantasy tropes, so there has to be a big battle!) a chunk of the mystery was revealed. It was not revealed in a big bunch of exposition. A crisis was reached, and in an act that resolved her internal conflict at the same time as saving one of her comrades (and temporarily thwarting the big bad), her true nature was revealed. I think it worked. It is currently in copy edit, and does not yet have a publication date, so I will have to wait for the readers’ verdict.
I’m a bit more nervous about the mysterious character in this one. He’s specifically hiding his identity for reasons that are both in character and important to the plot. He’s not a protagonist, he is helping one of the protagonists. Because he is specifically hiding his identity, and because his sub-plot is built around trying to protect a young woman who various people want dead, a lot of his scenes tend to be dark, grim affairs. I hope, when his identity is revealed, that the reader goes, “Oh! Oh! Why didn’t I realize that? Of course it’s ______!” rather than, “Yeah, yeah, we saw that coming a mile away…”
Wish me luck.