Benjen Stark (Joseph Mawle) was the mysterious man who saved Bran and Meera (Ellie Kendrick). If you don't count the younger version of him seen in flashbacks earlier this season, the last time we saw the grown Benjen was during the third episode of the show's first season.
The crazy thing is he has played a significant part on "Thrones," even in his absence. Jon Snow (Kit Harington) joined the Night's Watch because of Ned Stark's (Sean Bean) younger brother, who was a member of the Night's Watch. Soon after Jon started his training, Benjen left on a mission north of the Wall to explore reports of Wildling and White Walker activity. He never returned. Later, Jon was part of a search party for Benjen.
Olly (Brenock O'Connor) also used the lie of news about Benjen to lure Jon Snow to his death at the end of season five.
Now, he's back and sounds as if he will be pivotal in Bran's preparation to be the Three-Eyed Raven.