The powers that bound Eugene had been released and Eugene felt that he could harness the full potential of his abilities as the constraints were removed.
The Darkness had no choice but to prepare for the worse and fight Eugene after they defeat the Nephilim.
The Dark being couldn't leave the room but left lingering energy that was bound to the Okto-Khefali's dark head.
Eugene didn't fight off or made any attempts to eject the dark head. He knew that he needed the massive darkness to attack the Nephilim. But he was already plotting how he would detach himself from the control of the dark head when the time comes.
The two charged forward and left the dark room as its figure grew smaller to fit through the doors.
As he left, the darkness that was kept within the room exploded out and raced up the staircases.
Kyros sensed it and instantly contacted Mechiel to back away from the staircase and retreat in case the darkness separates.