They all ran away and left the fortress empty due to the spirited encouragement of their army commander.
Only the stubborn ones and the ones looting remained behind. They figured that Aeternus wouldn't care about them. They were right. He left the fortress untouched and resumed his journey.
He hadn't seen the end of the serpentine demon.
"What guts," Aeternus exclaimed when he saw the state of the next fortress.
The fortress was also deserted. The snake demon had come here straight from its fortress. It figured that since Aeternus was at its place, he couldn't be here. It initially came to see one of the other two demons in the alliance that was still alive so that they can plan and figure out their situation. He also wanted to know how the fight went.
The blade demoness didn't die fully in their fight with Aeternus. She had also set up a clone that was meant to revive her. The black blade placed in a huge drum of blood hidden within her fortress was supposed to grow after her death but things didn't go well with her.
She revived but the cause of her death wasn't so simple so it affected her revival. The attack that killed her wasn't some explosion, it was a chaotic version of a divine attack with both physical and spiritual components. It also had a lock-on property. The attack had followed the coordinates of the fraction of her soul to this point and attacked her newly revived body.
The blade demoness got a second to live before a dark beam pierced her soul. She didn't die because the attack was only a spent spiritual remnant. Most of the power of the attack had gone after the several clones that the beholder had in place. The beholder was the main target so the beam went after it first before digressing to deal with pests. It had weakened immensely and lost its physical components after the long journey. But a newly revived clone couldn't protect itself against it. The clone of the blade demoness became brain-dead.
She revived but she was brain-dead. So when the serpentine demon came visiting there was no one to receive it. He snooped around and figured she had gone into hiding.
"She must have been in a hurry for her to leave her things behind. That fight must have traumatized her." The serpentine demon shuddered at the recollection of Aeternus' figure.
It didn't want to meet Aeternus at all. So much was his fear of Aeternus that he was determined to leave the plane. But that didn't stop it from looting the fortress in the blade demoness' absence.
Then he shouted to the soldiers, "Run for your lives. We fought a calamity that is the ominous reaper and he killed almost everyone in our alliance. Your commander has run away now. You better save yourself."
It went to great effort to convince the soldiers of the fortress. So Aeternus came to a thoroughly empty fortress. There wasn't even any leftover because the soldiers had time to loot and the vice commanders had the opportunity to take what was left after the serpentine demon had had his pick. He didn't know that the blade demoness was still alive somewhere beneath the castle because he didn't bother to search. So he left angry and very disappointed.
He came upon a free-for-all when he reached the next fortress. Word of his actions was spreading among high-rank demons. The top dogs in charge of fortresses choose to watch. It was the opportunity seekers that were riled up. The availability of fortresses without owners meant a chance for high-rank demons without one.
The distance between each fortress is large, so there's time for different things to occur. It certainly is enough time for a free-for-all to occur when a certain serpentine demon is intent on spreading the news of their defeat to anyone that would listen.
His eyes lit up at the sight of 50 high-rank demons. He thought to himself, "What's not to like?"
In fact, free-for-alls have started in all the fortresses Aeternus had looted. Usually, the top dogs remain in control of their fortress until they become noble demons and have to move deeper into the plane but he had caused a shift in the hierarchy. There are a few openings now due to his actions. These openings will lead to competition and the reshuffling of power among high-rank demons. But that's not why he is happy.
"This is genius. I should have thought about this earlier. Bait is always needed if you need to catch a lot of prey. They will come to you."
The prospect of battle is why he is happy. These demons came here for his property. Courtesy demands that they don't leave here at all. It's basic demon conduct.
He didn't mind that they had set fire to the place and probably looted the place. He doesn't care about the things he is looting anyway. The things he has looted are of little use to him. He is just stockpiling them for when he creates his own army or noble family.
It is rare for high-rank demons to possess divinity of any kind, so what he has gotten can only improve his stats not his mark of sin. What he looted is almost useless to him. He prefers to kill high-rank demons because their highly developed mark of sin will nourish him better.
He would accept the trade of a fortress for so many high-rank demons any time. And yet here they are, more than 50 of them, fighting over something that isn't theirs. They are like a gift of water to a parched demon. If they are willing to die for something that isn't theirs, then they should be open to receiving aid from him in pushing them to their deaths.
His eyes observed them like a predator observes prey. He analysed the situation and determined that he has to do something different if he intends to grab all these prey.