All’s fair in love and Viking-alien war.
Somethings happening to Clara that we havent seen from her before: She doesnt want to leave the TARDIS.
Her fight or flight response is all fight, all the time.

Credit: BBC America
Is there any way to win?
(Clara, were going with the Vikings.)
She welcomes the warriors like family.
The Doctor tries again to win his captors respect, but yo-yos just arent what they used to be.
No one believes that hes Odin (Oh, and you would know how, exactly?
), and thats before an actual face appears in the clouds, claiming to be Odin.
Thats the thing about the gods, he says: They never actually show up.
Odin beams his army down to earth, where they hand-pick the Vikings best warriors and teleport them away.
A wall closes in, pushing them into a hallway thats ready to vaporize everyone.
The Viking warriors are killed, but Odin spares Clara and Ashildr, just as Clara expected.
Clara offers to let Odin leave (The universe is full of testosterone.
Trust me; its unbearable), but Ashildr isnt so willing to let this go.
Her people are dead, and she wants someone to pay for it.
The Mire are one of the deadliest warrior races in the galaxy.
(Details, c’mon.)
A baby cries nearby.
Do babies die with honor?
Courage itself isnt enough of an ideal.
Hes the Shang to Ashildrs Mulan.
And its obvious that Ashildr is the key.
Now hes got it.
NEXT: Isnt that wizard?
They electrocute the Mire, and a charge on the ceiling pulls off a few of their helmets.
The Doctor fits one on Ashildr, who dreams up a story: A serpent is after the Mire.
Ashildr tapped into their visors and made them all see what she saw.
Odin chooses door No.
But the Doctor couldnt save everyone.
He tells Clara that hes sick of losing.
I dont mean the war.
Ill lose any war you like.
Im sick of losing people.
Look at you, with your eyes and your never giving up and your anger and your kindness.
And every place I go, it will be there.
Which he cant or he can, technically, but he shouldnt.
Time travel has rules.
This is starting to sound familiar.
The Tenth Doctor had this exact argument with Donna in Pompeii.
She wanted to avoid the tragedy, but it was Pompeii or the world.
The Doctor remembers Donnas compromise Just save someone and understands why he chose this face: To remind me.
To hold me to the mark.
Im the Doctor, and I save people.
Do it for Donna.
Its possible that Ashildr has lost the ability to die.
(Dying is an ability; believe me.)
The Doctor knew that when he saved her its why he gave her a second repair kit.
He didnt want to sentence her to an eternity alone.
But he might still have created something bigger than he can control.
Winning is all about looking happier than the other guy, and Ashildr doesnt look too happy.