Unfortunately, the fate of the Celestial of Lightning is still sealed. It is just a level 4 Celestial while she is a level 5 demon king. The fact that it can now spot her and attack her directly doesn't remove the disadvantage of strength. It has only stopped the succubus queen from toying with it until it dies.
The succubus queen formed a barrier around her that protected her from the field of lightning and the target lightning strikes while she empowered her whip with more power to deal deadly blows. The level 4 defense of the Celestial couldn't save it from being threatened.
The level of Authority is not an absolute indicator of strength. A Celestial or a demon king with a level 4 Authority can harm and kill a Level 6 Celestial or demon king. It is all about opportunity and skill. Two fighters with two blades of varying lengths will have different chances of victory if they fight. It is obvious that the one who brought the knife to confront the other with a sword is at a disadvantage. But it has happened, though rarely, that the person with the knife wins the fight through the utilization of better skill or opportunity provided by plain luck.
A stronger Authority is like having a longer reach and a higher damage output. But skill is very important. So is the amount of enemies. A single level 4 demon king will have a lot of difficulties taking on a level 5 demon king much less one that is level 6. But two level 4 demon kings or three of them will surely have it easier to vanquish a level 6 demon king.
They are not like Aeternus. The body and soul of demon kings are separate. It has the advantage of preserving the bulk of their power when they die. The injuries of the body won't affect the soul. It is good since the Authority of a demon king is concentrated on their souls. Their body can be empowered by their divine rank energy and their Authority but it isn't like Aeternus whose body is literally made out of his Authority.
To Aeternus, the length of the knife doesn't matter, you will have to get through the tough armor that he is wearing. If your weapon is not good enough to overcome his defenses, then he doesn't even need to kill you with his own blade. He can bludgeon you to death with his armor-covered fist.
Aeternus faces some disadvantages too since his death leads to the loss of an entire level of Authority instead of just a single Celestial Godhood. If he somehow dies, his Authority will fall to level 9 immediately. He won't die since he is not here. So to be more precise, the Authority of the crown in this avatar will fall to level 4 while the other demon kings will still be at level 5 if they die once.
The Celestial of Lightning has a lower level of Authority and there's just one of it fighting the succubus queen. It doesn't have the advantage of a bigger weapon with a longer reach or higher damage output. And it doesn't have the assistance of others. So it was vanquished after a few minutes of fighting.
It fought admirably and with impressive tenacity. The element of lightning is highly destructive so it was able to critically injure the demon king of lust several times before it died. But that is all it managed to do before it succumbed to its injuries and fell apart.
The Celestial of Wind also suffered the same fate. It took a longer time for it to die since its near-formless tornado body could minimize damage from attacks to a certain level. It also couldn't damage the demon king of wrath because of the strong defense of its red scales. The two of them couldn't damage each other properly so their fight became a slugfest.
The Celestial of Wind formed several wind blades that rotated around itself to strike the snake demon. The snake demon also used his curved blades in an unrelenting pursuit to damage his foe. He struck at the Celestial of Wind in a frenzy fueled by agitation, anger, and excitement. He became a whirlwind of attack fighting against an actual tornado. They hit each other over and over again until one of them finally died.
The snake demon was severely injured by the time the fight ended. He had many open wounds leaking blood fire from his to the ground. Had the fight continued for a little while more, then he would have been the one to die not the Celestial of Wind.
The outcome of the fight would have also been entirely different had their opponents been different. The whip of the succubus wouldn't work against the Celestial of Wind because of its formless body and the snake demon king is too slow to threaten the Celestial of Lightning.
The destructive lightning would also be able to overpower the defense of the scales of the snake demon king. These things would have changed the outcome of the fight. So it is fortunate that the demon kings chose opponents that they can fight effectively.
Their decision of opponents was not by chance. It was according to the information that Aeternus supplied to them. They could have died without that information. It is obvious that Aeternus doesn't want them to die. He certainly didn't give them the information to ensure the success of the invasion. He can win on his own.
The succubus queen finished her fight first so she was watching by the side. The snake demon had roared valiantly into the air after his victory. He noticed that the succubus queen was giggling coquettishly at him.
"What so funny?" He asked with a growl.
"Nothing. You're just so manly. Very manly and very dominant." She replied with a wink.
The snake demon smirked. "Yes, I am very manly. It is high time you noticed it."
Then it began a sermon about how wrath makes a man and how violence should be the tool to solve every problem.