That day, a world-shaking battle unfolded beneath the skies over the Tanzawa Mountains in Kanagawa Prefecture.
It was a battle that would not have been an exaggeration even if it were recorded in the history books.
Terrifying magical power churned.
The Pitch Black Aurora spread.
The earth trembled without end.
Mountain after mountain was shaken.
A truly world-shaking battle was taking place here.
"Rumble...!"
As the source from which the battle had begun, a towering mountain seemed to be shattered by some astonishing force. It gradually came apart, collapsing into rolling rocks and clouds of dust as it sank into the ground, the rumbling never ceasing as it echoed through the air.
Within it, one astonishingly powerful Beast Vassal after another surrounded and attacked a gigantic tortoise-serpent demon beast, displaying terrifying destructive power.
Some of the vampires transformed into mist and appeared atop the surrounding mountain peaks, while others directly spread their magical wings and flew through the sky. All of them wore ecstatic smiles as their magical power ran rampant, surging forth with a roar and forming Beast Vassals that attacked the tortoise-serpent demon beast.
The tortoise-serpent demon beast roared continuously, the Pitch Black Aurora swirling around its body. It directly dissolved the attacks of one Beast Vassal after another, and even covered the Beast Vassals themselves, melting them away.
Whether the attacks launched by the Beast Vassals or the Beast Vassals themselves, all of them were formed from magical power.
Beast Vassals were originally condensations of magical power—the magical power itself given will. Against Otherworld Erosion, which could erase all magical power, they could not possibly inflict any damage. They could only be captured and eliminated one by one.
However, the vampires were not completely without means of fighting back.
"'Manas'! 'Utpala'!"
With a crazed smile, Vatra summoned