<human>:  Why did the Emperor give Vader the red saber?
<bot>: The Emperor gave Vader the red saber to remind him of his past as a Jedi knight. Vader was a former Jedi knight, but he had fallen to the dark side of the Force and become a Sith Lord. He had turned to the dark side and betrayed the Jedi Order. Vader had become a Sith Lord because he had killed his own son, Luke Skywalker.