There are classical roots to this character type, sometimes called the "Monster," and sometimes the "Other." In its simplest form, the Other is simple a character that is not welcome or suited to acceptable human society. More nuanced interpretations will explore how this difference makes it difficult for the protagonist to understand or even communicate with the character that is Other.
The modern trend toward themes like understanding and tolerance mean that this character type is often subverted for the "we're not so different after all" plot twist when the character's Otherness is central to the story or their characterization.
More traditionally, we see characters that are Other as outcasts from society or sometimes not human at all, being beyond human understanding or at least outside of their sphere of influence. Older examples would include the Minotaur in the Labyrinth or Media, the witch from the play of the same name.
More recently, we have characters like the Careers from The Hunger Games, Q from the Star Trek universe, and the monster from Frankenstein. These are all Other in different ways, but they are all Other nonetheless.
In The Hunger Games, the group called "the Careers" are those that have more training, more muscle, and more experience than the others. They're no longer considered victims like the rest of the kids thrown into the arena because they don't belong to that society.
Similarly, but on a different level, Star Trek introduced a character called "Q" in the Next Generation series. Q is a reality-warping, terrifyingly powerful character that causes all sorts of mischief, but is fascinated with the society to which he does not and cannot belong - that is, the human society of the Enterprise (and later, the Voyager and the Deep Space 9 station). Unlike the Careers, he is outside the society he's interacting with because he is incapable of being a part of it, not because of lifestyle.
Finally, we have Frankenstein's Monster (sometimes called "Adam" in urban fantasy translations). Like Q, he's excluded from human society because he's not human, but he is capable of partaking of the society he craves.
To break this down, these are three options for the Other:
- Leaves society by choice/through lifestyle
- Was never part of society and wants to join, but can't
- Wants to join society, but society actively rejects them
These aren't the only options by any stretch, and I'm sure some of you can think of examples for other methods to handle a character like this. In many stories, the Other serves as an antagonist because it's very easy to use the one outside the society as a basis for the "us vs. them" mentality. In other stories, it's the main character that is the Other. Either one of these can be a commentary on society and acceptance. The Other is very useful in providing contrast and an outside view of the main character's familiar worldview.
What characters do you know or like that are Other?