It is a common theme, these various methods through which a major or minor character is magically compelled to act against his or her will.
In the real world, mind control takes a lot more than magic, and a lot less than a hypnotist's pocket watch. The treatment of this topic from a scientific point of view would take much more than single blog post. Believe me, I've tried to fit it into a couple of posts, and could only cover the basics. In real life, psychological manipulation is not all-consuming, and it requires a long process to win trust, appeal to ideals, give the experience of group euphoria, and then slowly build a trap of fears, thought terminating cliches, and other mental tricks to keep the person from listening to reason. As difficult as it sounds, it is also appallingly common, and of course people who have been coercively persuaded don't even know it. That's sort of the point.
In fantasy, it's a lot easier. And much more glamorous, if you pardon the pun. Our villains have the advantage of magical prowess, so they can cut right to the chase. Unlike real life, their powers are all-consuming. They work 100% of the time, without fail, on anyone they choose. They can make people go against core beliefs, without the messy complications, or years of preparation.
We are all familiar with the black and white celluloid of Bela Lugosi compelling Renfield to leave the window open, the nurse to remove the protective wolfbane from around Mina's neck, and of him luring Mina herself out into the garden for his final bite. His power, like that of many other vampires, is part-magic, part-seduction... there is an theme that deep down, the victim wants to succumb. Something about the monster is irresistible. She already craves that which is forbidden, and the vampire uses this to his advantage.
Many vampire worlds contain another form of compulsory magic: the blood bond. Three sips of the vampire's blood, or in some cases, just one, is enough to completely take over your mind. The vampire now has a hold of you. He has earned your unquestioning loyalty and can command you to do anything. Even if you started the plot as his sworn enemy, it no longer matters. Your will is his.
The werewolf equivalent is pack dynamics. The Alpha has the magic ability to command and control all members of his pack, whether they like it or not. This is much less about seduction, and more about brute force. Perhaps you want to obey, because the pack leader is admirable, or out of a sense of tradition or duty. But when push comes to shove, none of that matters. Pack magic trumps all.
For the human villain, spells seem to do the trick. Themes of sympathetic magic are common in modern fiction. A witch or wizard can obtain a personal item or make a symbolic image, and through this, gain control over the victim's body, mind, or pain centers. These myths originate from a number of traditions, including European folk tales and the African practice of Vodun (often fictionalized as "Voodoo"). All it takes is a lock of hair, a lost button, or a captured tear to turn another human being into a puppet.
The Celtic peoples had a concept of part-oath, part-taboo, part-compulsion, called a geas or geis (pronounced something like "gesch"). A certain behavior would be proscribed or prescribed, and should that person fail, a dire consequence would ensue. A king could demand such a geas to ensure loyality from a warrior, or an old hag could use it as a curse. It could even be used as a means of protection, if for example, the person is compelled to never die except under very particular, supposedly impossible circumstances. In the famous Irish tale of Cú Chulainn, the hero is bound by geas to never eat dog meat. He has a second geas (actually a part of Celtic culture) compelling him to always accept hospitality. His enemies used these to create a double bind and defeat him. He is offered dog meat, and being forced to accept it, he becomes weakened enough to be defeated in battle.
A love potion can make anyone fall in love, which is quite an act of compulsion, especially since love itself is arguably a form of compulsory magic. A love potion is created by a scorned admirer to force the object of her affection to requite. In the typical tale, the potion backfires, causing the subject to fall in love with a squirrel, a rival, or "a cop down on 34th and Vine".
Faeries have it easy when it comes to mind control. Whenever the mortal wanders into the faerie glen, or stumbles upon the faerie banquet in the basement, you can always bet they will be tempted into eating the fairy food. After that, there is no escape.
Originally, the zombie was another form of magical mind control. While most modern zombies are dead or diseased people acting on their own with a built-in, single-minded compulsion for brains or killing, the original zombie was an undead puppet of a magical shaman. This interpretation lives on in our metaphorical language, when we refer to TV viewers or mall shoppers as "zombies".
Demonic possession is perhaps the most terrifying form of supernatural mind control. In this case, the monster lives inside the victim, mind and body given over entirely to the demon's will.
Resisting mind control in real life involves a constant skeptical mind and persistent mistrust of even the nicest people. In fiction, mind control is often inescapable. When dealing with faeries or magical tricksters, the best bet is to never agree to anything. And never eat the fairy food! Or drink any suspicious potions labeled "#9". When dealing with vampires, the best bet is to immediately deploy a wooden stake. Wards are said to combat sympathetic magic, or you can simply become OCD about never letting your possessions out of your site (lest you become one yourself). Religion is said to combat demons, and if you never give your soul to a bokor, you probably won't become a zombie.
But when it comes to resisting mind control, magical or otherwise, perhaps Jennifer Connelly said it best when facing down the Goblin King:
For my will is as strong as yours, my kingdom as great. You have no power over me.
What are your favorite mind control powers in urban fantasy?