After an intense, action-packed and larger than life two-parter, "Doctor Who" season 9 will see the Time Lord and Clara face what the latter found out as the "deadliest warrior race in the galaxy." This also marks the entrance of "Game of Thrones" star Maisie Williams.

As seen in the trailer, the Doctor sulks upon realizing that they landed at a small Viking village where the mercenaries called the Mire abound. There, they meet a young girl named Ashildr, who made a big mistake of challenging the breed of dangerous space warriors to a battle.

The Doctor, Clara and Ashildr only have 12 hours to make fighters out of farmers in a bid to win the war. Sadly, even though they miraculously pull that off, they are desperately outnumbered and outgunned, as the synopsis for the "Doctor Who" season 9 episode ominously teases.

This puts them in an extremely precarious position and their fate seems to be very clear to themselves – and it does not look good. Relentless and hard-hearted, these Vikings are a force to be reckoned with and until each of their enemies is down and dead, they won't stop.

In the face of the life-or-death crisis, the Time Lord is lost in thought about Ashildr's odd familiarity. He feels like he has seen this young Viking girl before but he can't quite put a finger on it. But fans will discover soon in this "Doctor Who" season 9 episode.

As teased in the "Doctor Who" special Radio Times magazine, this will be the very installment "the Doctor remembers where he's seen his own face before." What that truly means will be fully revealed in the episode, which is portentously titled "The Girl Who Died."

As already hinted by executive producer Steven Moffat, Williams' character is not a returning character but actually a new one. And fans will find out what she is all about on Oct. 17, when "Doctor Who" season 9 episode 5 airs on BBC One.