Things are going well for Viron. His opponent couldn't deflect his fireball spell well, so he is running away. But how could Viron let him go? He gave chase while bombarding Aeternus with fireballs.
"What did I expect from a low-rank demon? You killed some ignorant mid-rank demons and you think you are some big shot. You will fall to the might of my spells." Viron proclaimed grandly.
He shot more fireballs but they were slow and easily dodged. So he used fire bolts to catch his opponent's attention. Whenever Aeternus stops to deflect the fire bolt, a fireball will be close and ready. But even that didn't stomp Aeternus. He would just deflect the fire bolt towards the fireballs and detonate them away from himself.
Viron tsked. "This demon is tricky to deal with. Will I just let him go? I have to use it."
He was a little impressed with this skillful low-rank demon. His caution, reaction, and judgment were top-notch. They weren't things a measly low-rank demon should have and it was making Viron's fight difficult and his objective impossible to achieve.
His spells weren't working and Aeternus was faster than a low-rank demon should be capable of. He didn't want to let Aeternus escape. So he decided to use his trump card. Fire mana left his mana core through his energy vessels into his heart where his sin energy is stored. It mixed with a little sin energy before it entered the atmosphere where it began to form a cloud of fire.
The cloud will continue to siphon his mana until it is fully formed. This is a spell that will take his full attention and needs time to be cast. Such restriction means he doesn't use it often in fights with other demons, not even when they are his allies. Casting the spell makes him too vulnerable for his liking. But it is something he can get away with since his enemy is running away from him.
The spell will also leave him drained of mana after casting it. Such a spell should be beyond his rank but he has his sin ability to thank for his ability to cast it. Once the fire cloud is formed, next comes fire rain. Drops of fire will fall like hailstones and deal damage over a wide area. He would be able to control the cloud and use it to chase down his opponent to death.
"What?" He shouted in surprise when Aeternus began to run toward him instead of away from him.
He tried to back up while casting the spell. He should be able to finish casting it before Aeternus reaches him. Letting go of his spell right now will lead to a backlash. Aeternus picked up a rock, doused it in chaos flames a little, then threw it at Viron. Viron tried to remain calm when he should be panicking. He had never been able to double cast while he is casting the fire rain spell. He knew immediately that if he doesn't conjure a shield right now, he would die, and panicking will not help him in any way.
So he was calm. He focused and the threat of death helped to push him above his limits. A shield flickered into existence just in time to stop the projectile of death. It cost him some delay in the casting time and a small loss in the progress of the formation of the spell but he did it. He felt exhilarated.
That was before he saw what was going on with Aeternus. Aeternus' claymore was now coated in the same black flames that covered his body. Then he swung the claymore towards the forming clouds. A curved streak of black energy flew from his chaos vessel and entered the fire cloud. The cloud expanded before exploding.
"Argh..." Viron screamed in pain as his spell was torn apart.
It felt like his mind had been torn apart too. The backlash he was experiencing is worse than if he had let the spell go himself. He fell on his butt, mentally and mana drained. But his opponent is still rushing towards him with that darkened claymore of his. He didn't need his years of experience as a mid-rank demon to know that he had to do something or he would be killed.
Viron tried and tried but it felt like his mind was in shambles and incapable of pulling the mental prowess needed for the complicated visualization required for spellcasting. But he didn't give up or panic. Then he succeeded when Aeternus was only three meters away from him.
A fireball sprung into existence and shot toward his opponent. It would be difficult, maybe impossible for Aeternus to dodge it at this distance. Deflecting it will also cause it to explode and the short distance will ensure that it catches both of them. Viron was willing to pay the price as long as he lived.
Aeternus was not. He swung his claymore and cut through the fireball. The fireball split into two and He flew through the middle toward Viron. His blade loped off Viron's head which was still wearing a look of utter disbelief on it. The two halves of the fireball spell winked out of existence just as Viron's life did.
"Impressive." Aeternus complimented Viron after his death.
The fight was thrilling for Aeternus. Viron had shown him what the best mid-rank demons are capable of. He couldn't cast spells but his weapon could shoot out blades of chaos flames. When he combined it with the knowledge that chaos destabilizes spells, he got an idea about how to overcome his opponent. He was just waiting for the right time.
The right time he was waiting for is when Viron runs out of mana, which he can check since he could see Viron's stats. But it didn't seem like it would come when Viron was using the fireball. He might make a mistake and die so he decided to retreat.