in the star-wars movie Luke is training with Yoda on Degaba and at one point he goes near an area and tells Yoda he feels COLD. Yoda proceeds to tell him that the area (which has a cave ) is strong with the DarkSide. When Luke proceeds to the area with his weapon Yoda tells him he wont need it but Luke doesn't listen and takes weapons anyways. When he enters the cave he see's Vader and they fight. He kills Vader and destroys his mask to reveal it Luke himself behind the mask.
I went a little over-baord here but it's got to be linked to this part of the movie.......Maybe???
When Luke Skywalker traveled to Dagobah to train with Yoda in 3 ABY, the elder Master tasked him to enter the cave. Luke confronted an illusion of Darth Vader within and defeated it in a lightsaber duel, dipping into the passion of the dark side in the process. It was there that he realized what would happen if he turned to the dark side of the Force. Behind the mask of Darth Vader, he saw his own face. It also presaged the revelation that Vader was, unknown to him at the time, actually his father, Anakin Skywalker.
"That place… is strong with the dark side of the Force. A domain of evil it is. In you must go."
"What's in there?"
"Only what you take with you."
―Yoda and Luke Skywalker