I tried to come up with a story that spreads through all the songs in the album:
1- the people must protect the wall from the invaders (Senjutsu).
2- they need to come up with a good strategy quickly, because the war has already begun (Stratego).
3- the end is inevitable (The Writing On The Wall).
4- their world seems to be lost and they started to feel like they are lost too (Lost In A Lost World).
5- their future is long gone (Days Of Future Past).
6- they wished they had a time machine to turn back time, thus they would have been more prepared for their fateful battle (The Time Machine).
7- the darkest hour has occurred for them (Darkest Hour).
8- they asked for help from other tribes, but even the Celts were not enough to repel the threat (Death Of The Celts).
9- they read some tactics written in the parchment from the history of their ancestors, but it was too late (The Parchment).
10- perhaps all hope is lost, hell is on earth, but they will not surrender. Could it all be just a dream or their world is conquered from within... (Hell On Earth).