Game of Thrones Season 6 Episode 06 Blood of My Blood
Bran awakens to find the rider is his uncle, Benjen Stark, who had gone missing beyond the Wall. Benjen explains that he was stabbed by a White Walker during a ranging and was left to die, but was saved by the Children of the Forest by being impaled with dragonglass. He tells Bran that he needs to become the Three-Eyed Raven and control his warging before the Night King comes south.
BRAN: Who are you? Uncle Benjen. The last letter Jon wrote me said you had been lost beyond the Wall.
BENJEN: I led a ranging party deep into the North to find white walkers. They found us. A white walker stabbed me in the gut with a sword of ice. Left me there to die. To turn. The Children found me. Stopped the walker’s magic from taking hold.
BENJEN: The same way they made the walkers in the first place. You saw it yourself.
BRAN: Dragonglass. A shard of dragonglass plunged into your heart.
BENJEN: You are the Three-Eyed Raven now.
BRAN: I didn’t have time to learn. I can’t control anything.
BENJEN: You must learn to control it before the Night King comes. Drink. One way or another, he will find his way to the world of men. When he does, you will be there waiting for him. And you will be ready.
Source text: Wikipedia.