Tales of Vesperia: The First Strike

S1, E1: In a mythical kingdom, the Imperial Knights harness a magical substance known as Aer to protect humanity from the monsters of the forest. But the Aer is somehow changing, causing the wilderness to waste away and stirring the woodland beasts to attack with greater frequency. As danger creeps steadily closer to civilization, two young recruits must uncover the truth behind the transforming Aer.