They can't stay close together or they will risk Aeternus taking out more of them with a single shot. So the remaining Celestials stayed in a loose mobile formation with a wide distance between each of them. They were able to stop themselves from panicking and reforming their forces just in time for Aeternus to collide with them.
The Celestials had scattered earlier when the beam hit their formation. They ran for their lives from the black beam of death. That made them stop paying attention to their attacks. Aeternus kept them busy with escaping with their lives while he expanded the pathway created by the beam. He used his normal attacks to destroy the obstacles in his way and quickly reached the Celestials.
The beam was on for a total of 5 seconds before it was shut off. It is a short amount of time but it is very long in a fight of their level. Aeternus had become too close to be rebuffed by the time the beam was off. So they could only reform and clash with him. Their mission is still on. It is just that they are on a very short time limit. They have to eliminate the demon kings quickly so that they can help the four downed Celestials recover.
The Celestial of Earth is at the head of their new formation. He is the one with the strongest defense after the Celestial of Metal. So he was the one who clashed with Aeternus in close quarters. The remaining five will support him with ranged attacks.
If done well, they can still kill Aeternus fast enough. Or so they thought. Aeternus allowed his Chaos energy to enter the world around him in the form of a domain.
A black cloud suddenly exploded out of him. His Chaos energy is always ready to rampage but he has been holding it back. So it is very eager now that it has been given permission. It covered all the Celestials quickly robbing them of their sight and senses. The Celestials finally panicked.
They had been on edge because of the beam of death. Then this happened. It seems to them that the world suddenly darkened and became hostile to them. A corrosive energy enveloped them. It began to tear into them. This finally made them panic. They scattered in every direction looking for a way out.
The round ball of reinforced rock didn't know what hit it. The Celestial of Earth couldn't see anything in the shroud of darkness. All it knew was that Aeternus was supposed to be in front of it. So it attacked its front with all its might. Earth spikes and boulders assaulted where Aeternus should've been. Unfortunately for it, it did no good.
Aeternus saw everything that happened. He could have dodged the attacks. He could have circled sideways and attacked his blind foe from the left or right. But he didn't because he doesn't need to.
He went straight through the attacks fearlessly. They struck his body harmlessly as he passed through them. He swatted aside the ones that blocked his way. Then he got close to the Celestial of Earth and cut into it with all four of his claymores.
"Arrrrrrrr." The Celestial of Earth screamed in pain.
His arms slashed and a Celestial screamed. It was a soundless scream. Both sound and spiritual transmissions cannot go through this cloud of Chaos energy. So no one saw or heard the Celestial of Earth die.
It was a swift but very painful death. Aeternus cut into the ball several times until the sphere broke down. The Celestial of Earth was helpless against him. It couldn't do anything to defend itself. It was blind and its attacks are useless against Aeternus.
The structural integrity of the Celestial of Earth's body and mind was severely compromised by its injuries. It couldn't take any more so its existence collapsed. A brown sphere glowing with a subdued light appeared from the remnants of the Carved up body of the Celestial of Earth. It signified the death of a Celestial.
Aeternus took the Celestial Godhood that appeared and kept it in his personal space. It is a space created by his Authority and attached to his soul. It is not the inventory given to him by the realm lord. He doesn't trust the realm lord enough to keep his things there.
Then he turned his attention to the other fleeing Celestials. He wielded his powerful soul force to form three chains and swung the chains at three separate Celestials. The chains wrapped around the three Celestials. Then he pulled them back to him and he proceeded to massacre them.
It was a slaughter. That's the only thing that it can be called. It was not a fight. A fight needs substantial resistance. These Celestials couldn't put up any worthy resistance so it was not a fight. They are no different from choice meat being carved up and devoured in the most ruthless way possible.
This outcome is not an unexpected scenario since this avatar of Aeternus has the strength of a level 10 demon king. Level 10 is the highest level of Authority that a demon king can have. That means that he has reached the requirement to become a demon god. The attack that took out 4 Celestials at once is not his trump card. It is just a casual attack.
None of the Celestials can threaten him. They can't harm him alone or together even if they attack all day long. His body is made out of his Authority so it will require a level 10 Authority to even scratch it.
Other demon kings are not like this. Their body and souls are separate entities. Their Authority only empowers their attacks, sin abilities, and spells. It doesn't reinforce their body like his. It is a perk of having his body warped by Chaos energy ever since he was an unborn demon. So his body is created out of his Authority since he has the Authority of Chaos.