Morgen is a creature that people used to believe in a long time ago. It doesn't really exist.
Morgen is supposed to be a kind of fairy, like Tinkerbell, but not as nice. She could look like a beautiful lady with long hair and a tail, or like a sea monster. People thought she lived in water, like a lake or a river.
But even though she was pretty, people didn't trust her. They thought she would sometimes trick people into drowning in the water or into following her to a different world.
Today, people don't really believe that Morgen exists, but sometimes people still tell stories about her to have fun, like when we watch a movie with a scary monster but we know it's not real.