The Quest of the Golden Fleece
When the entrance of the Black Sea, it was blocked by clashing rocks. Syrus and his daughter Midia would give Jason the golden fleece because they were witches. But they would give it to him only if he took the golden fleece from the dragon, and if he would take the witch back with him and marry her. So the witch put a spell on the dragon to make it fall asleep. Jason climbed a tree to get the golden fleece off the dragon. But the spell didn't last long, because the dragon woke up and saw that the fleece was gone. Then the dragon saw the boat that Jason and the witch sailed away on. When they returned to Greece Jason had to marry the witch like he promised.