Basically, this is a visualization of the lyrics of “Senjutsu” (mainly the first two verses and the chorus) by Iron Maiden, from the album Senjutsu.

Beat the warning, the sound of the drums
Set the beacons afire for them all
Call to arms all the men far and wide
Have to fight now for dynasty, pride at stake

The invaders repel from the north
Keep out nomads who came from the plains
Northern grasslands awash with them all
Blocking the tribes that invade from the south of us

Rallying round to the call
We can hear, far away are the sound of distant drums
And they need everyone at the wall
So the day of our judgement has now begun to fall



Just because.