Mace is like a big stick with a heavy ball at the end that people used a long time ago to protect themselves or to fight against their enemies. You can imagine it like when you have a ball on a string and you spin it around and around, then you let it go and it hits something really hard. Mace works the same way, but instead of using a string, the ball is attached to a stick that you hold with your hand. When you swing the mace, the ball at the end goes really fast and can hit someone really hard, making them hurt or fall down. Because mace is so strong and dangerous, people don't use it very much anymore. Instead, they use other weapons that are safer and easier to control.