A warlock is the male equivalent of a witch or sorcerer. Your favorite fantasy novel might feature a wicked warlock who uses magic to take control of a peaceful kingdom.
In fairy tales, myths, and other stories, there are many types of fanciful creatures and monsters, such as unicorns, goblins, and vampires. Another is the warlock, which is usually a male witch. Just as a witch uses magic — witchcraft — so does a warlock. This word most commonly has a negative connotation — that is, in literature, television, and film, a warlock is usually a villainous character (unlike, say, a wizard).