The moment Aethara tried to kill Selene with a casual swing of her sword, Corey was able to react on time because his mind was entirely on Aethara and every single movement she made.
Although he had been taking his gaze off her, his Eyes of Omniscience provided him a birds eye view of everything that was happening in a hundred meter radius at the bare minimum.
Because of this, he was able to react to Aethara's sudden attack, and he pushed Selene out of the way while using his axe to block Aethara's saber.
To his slight disbelief and surprise, the force and strength behind her attack was more than he expected and he was sent flying away despite blocking the attack.
Through the birds eye view of his Eyes of Omniscience, he saw himself fly toward Selene and then he crashed into her, her body taking the brunt of the impact.
Damn it. I've said it before, following Master is really bad for my mental and physical health.'
Unedited chapter