Looks like our brave soldiers had a captain with some kung fu skill after all. And yes you are correct after reading this that there is a “Great Wall” keeping out the undead.  I did come up with this thinking of the Great Wall of China.  I thought it would be super cool to see Soldiers defending the wall from armies of undead.  Then I realized, Game of Thrones was also doing that… so I moved it from the north to the west.  So now it’s totally different.  😉  Okay, but consider that the Great Wall of China kept out large hordes of wild northern barbarians long before George R. R. Martin, so… there. 😉