The 13th Warrior
It seems that they copied ideas from The 13th Warrior. For instance, when the wraiths are attacking the fort, the woman pulls out some knives rolled up in a cloth and states "Don't let them take the children". This is the same scene from The 13th Warrior. The entire idea seems to copy The 13th warrior. There is even a cave where he has to go in where the evil is.
Si vis pacem, para bellum.