The Lady Archetype
The Bright LadyThe Bright Lady is a woman of rank, often a Queen, Princess, other nobility or of otherwise high rank. Occasionally she will be a maiden of low rank, having significant beauty, kindness and grace whom the Knight has found admirable and worthy of his service. To the Knight she is a force of goodness and a vision of Incorruptible Pure Pureness, at least by the end. Sometimes she grows into this over time, at first being haughty and prideful, indistinguishable from any other stuffy lady of rank, but eventually her inner goodness and worth is revealed. She listens and respects her Knight's opinions and will often defer to him, if he is more knowledgeable about something, or proves to be correct in something she had previously disagreed with. Very often there is a Bodyguard Crush involved. The Bright Lady's power usually lies in arenas outside of physical combat, for which she must rely upon her Knight for protection. In a fantasy work she may have magic (often not strong or recently discovered) which allows her to fight if necessary, or provide support or healing during and after one, but in non-magic universes she will be a Non-Action Guy, though this is increasingly subverted. Just as likely she is The Woman Wearing the Queenly Mask who must use her wits to survive in the cut-throat court politics going on around her. If she has a goal, other than escaping some evil lord who wants her dead, it's often recovering her title or noble position.
The Bright Lady also has a Shadow Archetype:
The Dark LadyLike her bright counterpart, the Dark Lady is a woman of high status. She may have inherited her position, but just as likely she has accumulated power with cunning, and even dark magic, and clawed her way to significance through the use of that power. It is not unusual for her to be a Femme Fatale who has recruited her Knight via manipulation, blackmail or Mind Control. She is often an antagonist, even a Villain, and where The Bright Lady will grow out of her arrogance and haughtiness, the Dark Lady on the other hand will usually become increasingly arrogant and controlling. Rather than her inner goodness being revealed, her inner evil will be revealed. She may listen to her Knight, though rarely goes out of her way to consult him, but in the end her orders are law, and will not take those orders being disregarded well. Just because she's usually the Villain however, doesn't mean she's always heartless. She may have her own deep affections for her Knight and sometimes they are lovers. The Dark Lady also tends to shun physical combat herself, but is much more likely to be a Lady of Black Magic or Vain Sorceress, wielding powerful and dangerous magic, and unafraid to use them at need. She usually wins, too. Unlike the Bright Lady, she and her Knight aren't always seen together, however and don't always fight as a team. And where her bright counterpart is often in the thick of things, needing to be protected, the Dark Lady is often commanding her Knight from the shadows, nowhere near any danger. Like the Bright Lady she uses cunning to get her way and may be involved in long term machinations for more power or even the throne.
The Knight Archetype
The White KnightThe White Knight has pledged his service to the lady and acts as The Champion to her. He has sworn his service to her above all else, not the country or some other greater organization, but dedicating himself solely to her protection and the furthering of her goals. At times his loyalty to his Lady and his other responsibilities might clash but you can bet in the end he will Always Save the Girl. In fact often he places his Lady's safety above even her wishes, and will openly and shamelessly defy her in order to protect her, and not regret it one whit. He is usually a man of high moral caliber, who follows a code of chivalry, but it's not absolutely necessity. The White Knight, even if he starts out a bit grey, will inevitably find himself doing good because his Lady acts as his Morality Chain. He is not always an actual Knight, or even a properly trained warrior, but he will be a Badass in some capacity, because he will have to fight for his Lady at some point. In a fantasy setting, if he doesn't start out as a ranking Knight, usually he is Knighted by her or someone else at some point and has the title in truth. He is usually the Lady's social inferior, which can be a problem if he becomes a Love Interest in a Bodyguard Crush situation, the same if she's a peasant maiden and he a nobleman, though, which happens occasionally. In older works it was just as common or more common for their relationship to be one of Courtly Love.
The White Knight also has a Shadow Archetype:
The Black KnightThe Black Knight often starts out as a White Knight, but under a Dark Lady's influence, that doesn't last long. So devoted to his Lady is he that he will sacrifice anything, including his honor, pride and values, to serve her as she sees fit. He may be just as unfettered as she is, eager to fulfill his duty to her, or he might feel uneasy with what she asks him to do, but his main feelings on it are usually My Master, Right or Wrong. If she is the Villain, he is her Dragon. There is no need for the Lady to ever be suspicious of him, she trusts him implicitly though occasionally, she probably shouldn't have. Still, it's rare that he would defy her orders, even to protect her, if she insisted hard enough. As much as the Lady values him, it's not unheard of for a Dark Lady to orchestrate her Knight's death if he displeases her enough. The Black Knight and his Lady are very often involved romantically, or one of the two wants to be. In fact it's not uncommon for the Black Knight to come to pledge himself to his Lady because of her active seduction. Neither is it uncommon for her to keep him by her side through blackmail, tricks, spells or other underhanded means, and in fact he may be the Brainwashed White Knight of a Bright Lady, usually the protagonist. That isn't to say that there are never instances of the two sharing true love, though, it's just less common. Usually he is a ranking Knight, Nobleman or other well-renowned individual of great skill, and almost never someone of low rank. The Dark Lady will only accept the best.