His voice sounded like the peals of judgement. "I told you, if you're useless to me, you will die. Now I'll give you a chance. You either succeed or you die trying."
He created a ball of chaos in his hands. It was like an orb created with a dark exterior material but containing a bright white substance shining from within. He understands it to be the chaos spark, a feature under his Oath of the Chaos Lord's ability. It can be given to anyone but it can be refused if that person is unwilling to be his subordinate. To receive it, the demon must swear an oath of allegiance to him.
He asked her. "Will you serve me?"
The snake spoke as it saw the dangerous looking ball that Aeternus is offering it. "Xander will do anything to grow stronger. Anything at all."
"Then take it. Either you evolve and become of use to me or you die."
He let the ball float to the demonic beast and she swallowed it. He would have killed her if she refused.
Then she went into hibernation as she began to evolve. A cocoon of Chaos energy formed around her. Accepting the spark of chaos will supplement all the requirements for the mark of sin and make the demons that accept it ready to evolve.
It also comes with very dangerous side effects. Chaos energy doesn't play nice. He has reduced its potency but it will surely run amok within the individual that accepts it. So being pushed into evolution isn't exactly a good thing. Evolution is the only way to survive the Chaos energy. They have to evolve and adapt to it just like his body did or they will die.
He waited patiently as Xander evolved. He sensed resistance at first before it disappeared. Chaos energy rampaged through her body like a wild horse but they were ultimately compatible. She has an affinity to darkness, one of the laws he used to restrain his Chaos energy.
It is an affinity to the element of darkness, not the law but it created room for the assimilation of chaos energy. She didn't have a complete soul, the lack of a mark of sin allowed chaos energy to gain full access to her soul. It just so happened that his restraint on chaos energy is soul related.
The combination of room for assimilation with chaos energy and the restraint of Chaos energy by soul concept worked in her favor. It allowed her existence to accept and evolve with chaos energy. If she didn't have both of the advantageous conditions then she would have died. Her willpower is too weak to present any resistance to chaos energy without assistance.
Her body began to change within the cocoon as she evolved. Xander grew larger and longer. She reached 100 meters in length and more than 5 meters in width. The horn stubs on the head grew into two horns more than 2 meters long. Her small wings enlarged into a structure 15 meters long.
She still has a flesh and blood body but it isn't a normal body. There are some influences of Chaos energy such as the black scales on her body becoming smoky and oozing black fumes
Chaos energy was leaving him through their connection to fuel Xander's evolution. The more powerful she grew, the more Chaos energy she consumed and the larger the cocoon got but he doesn't mind the energy usage.
He shouldn't be able to use the Oath of the Lord without control of the energy well but he had infinite energy and at a higher quality too. That's why he was given a unique one named the Oath of the Chaos Lord. So he doesn't mind the energy consumption. Even if he did mind and energy is scarce, he could always get it back by killing Xander if she isn't useful.
"Since I am a lord, and a better one too, I should assemble my forces. Plus I need an army to help out Legion-4." He thought to himself as he waited.
The Oath of the Lord is an ability that allows a subordinate to evolve while also strengthening the Lord. The Oath of the Chaos Lord is stronger than the demon lord's because the energy he supplies is at the half-divine rank. The demon lord is at the half-divine rank but she doesn't have an infinite amount of it to distribute. She can only give her subordinates the extreme energy rank that she has through the energy well.
She can help high-rank demons evolve into demon nobles if they submit to her. But their path will end there and they will be forever reliant on her for growth. If she doesn't grow stronger, then they will stagnate too. Her ability can't help demon nobles to evolve because only one person can receive the amplification of the energy well. But he can do that.
He can make high-rank demons and demon nobles become demon lords. That's why he didn't consider her a threat at all while she was threatening him. He respects her is not afraid of her, at least not anymore.
She had started watching him when he was about to be ambushed by the ten mid-rank demons. He was afraid of her attention back then. He was afraid of the manipulation of a high-rank demon, that's why he avoided the ambush. His fear for her was greater.
But things have changed. He is no longer afraid of her. He didn't have the strength to face her back then, but things her changing rapidly. He is not the little low-rank demon that was spooked by the attention of the demon lord or the mid-rank demon that ran straight into her ambush.
In fact, it's the other way around, she now fears him a little. He is more than prey to her now. Still, he will remain wary of her because of the respect he has for her. She may not be able to do anything to him directly right now, but underestimating her is folly and will lead to his downfall.