This is one of the few character types I know of that cannot be one of the good guys.
While not necessarily a villain (remind me to do up an article about the differences between an antagonist and a villain at some point) the Black Knight is rarely a protagonist and hardly ever a good guy. When translated to a good guy, the Black Knight loses part of what makes him a Black Knight and more commonly resolves into the Rebel, the Redeemed Villain, or the Knight in Shining Armor.
Some of the defining characteristics of a Black Knight are as follows:
- Enjoys (and is good at) fighting
- Unclear or doubtful allegiance
- Is associated with some form of moral code
This last point is a little squishier than the others, so let's dig into it.
Like the original Black Knights from medieval England, the knight is associated with a honor code in the public consciousness. The Black Knight is a perversion of this, usually being someone who wants to live up to the code but fails, or one who has explicitly broken that code. In most cases, the Black Knight still wears the outfit or wields the weapon or uses the title/name that ties him to the code, and may even obey it under certain circumstances. This isn't a necessary trait, but it is a common one, and can make for some fun knife-twisting in a plot where the main character expects the Black Knight to act a particular way, and he doesn't.
In addition, because of the Black Knight's ambiguous loyalty, it can be played as "this character is blatantly a bad guy, but doesn't work with the Bad Guys" or "this character is neutral to the big conflict and sometimes helps the main character for whatever self-serving reason."
There are some occasions where the Black Knight is serving as the Big Bad's powerhouse, and in those situations, since the Black Knight is a pawn rather than his own master, he can be replaced with the Brainwashed Best Friend, which also has some awesome knife-twisting potential. (Think about Bucky from Captain America - definitely a Black Knight.)
Can you think of any common qualities the Black Knight has that I missed?