The black robed figure's body was split in two after being hit by Michael's slash. It doesn't fall right away; Instead, it remained standing in its place stiffly.
All of the Celestials presents stared in awe, their eyes widening and their foreheads furrowing as they stared at the sight. They finally saw that a Celestial could actually kill the black-robed figure without any problems.
The black-robed figure was indeed quite a bit stronger than the ordinary monsters that had come out of the walls; but by no means strong enough to kill or even injure them - Celestials.
A moment later, the black robed figure's body which had been split in two began to dissipate into a black mist. The black mist evaporated into the air and flew back towards the black wall.