This sentence explains about Darth Vader. He is an enemy of Luke Skywalker. But he was a soldier of Jedi, so he was a friend of Jadi. He was called Anakin Skywalker in a soldier of Jedi. He He has fought Sis, but he listened to prediction of the death of his wife by Sis. After that, he went over to the Sis side, and he got name "Darth Vader". He leads Storm Truper which is the corp of empire.