When Anastasia felt a thick black aura enveloping President Aiden, she agreed with the principal's opinion about President Aiden who was already under the influence of a demon.
Even the visible Ragnor was clearly a demon, however, he did not emit a monstrous, pitch-black aura, like President Aiden's around his body.
Inevitably, it was the act of the Behemoth's Order which was able to harness demonic energy into a human's body and turn it into a deadly combat weapon.
It sounded tantalizing, because humans could gain immense power instantly, but everything related to demons such as strength, were of course not given freely, there were things they needed to pay to be able to use that power.