Watching the explosion, Sylas was secretly pleased. The fireball technique from his Fire Control ability had impressive power. And this was just a level one skill—its power would only increase as it leveled up.
Sylas conjured another fireball and threw it. It transformed into a rocket, targeting a group of zombies on the street. The fireball exploded one meter above the zombies, this time under Sylas's deliberate control.
Sylas realized he had some control over the fireball, such as slightly altering its flight path or controlling the timing of its explosion. He knew that an airburst explosion had a greater impact than one that detonated on the ground. So, he made the fireball explode above the zombies.
The explosion's power was comparable to that of a bomb. The fireball's detonation killed a dozen zombies below, blasting their heads apart. Several dozen more zombies were injured by the blast. The explosion generated not only a powerful shockwave but also intense heat. Sylas saw the zombies caught in the blast being burned by the flames. If they had been human, they would have been turned to charcoal, even if they survived the initial blast.
The explosion of just one fireball had an incredibly devastating effect.
"This fireball is truly powerful," Sylas marveled.
However, he noted that using the fireball technique also required a significant amount of energy.
Sylas could feel that every time he used the fireball technique, a bit of energy was drawn from his body. This was an indescribable force, and as it drained, Sylas felt mentally fatigued. Checking the system interface, he realized that using Fire Control consumed his mental energy. His current mental strength was not robust enough to withstand heavy usage.
Sylas estimated that in his current state, he could use the fireball technique seven or eight times before it began to take a toll on his body. Besides the fireball, he could also shoot high-temperature flames from his hands. However, the flame jet lacked the explosive effect and consumed more energy, making it less efficient than the fireball technique.
After casting two more fireballs and annihilating a large group of zombies, Sylas felt exhilarated. Unfortunately, despite killing so many zombies, there was no movement in the skill's energy bar. It was clear that these zombies did not provide the required energy for the upgrade.
Sylas frowned, feeling frustrated. The system didn't directly inform him of the conditions needed to upgrade the skill. How long would it take to find the correct method through trial and error?
At that moment, a loud roar echoed. A massive mutant zombie appeared, approaching with a growl. Seeing this gigantic mutant zombie, Sylas suddenly had an idea. Perhaps killing such a powerful zombie was what he needed to upgrade Fire Control.
With this thought, Sylas decided to test his theory. After all, he wouldn't know unless he tried. The mutant zombie was stomping towards the explosion site, likely attracted by the noise. Sylas began to form a fireball in his hand, concentrating and charging it.
The power of the fireball grew stronger, and its color deepened. However, Sylas didn't feel any heat, instead, he felt a chill. This was because the fireball absorbed all the surrounding heat, making the area feel cold.
Reaching its limit, Sylas hurled the fireball, which flew straight at the mutant zombie's head. He didn't make the fireball explode prematurely; instead, he let it hit the zombie's head before detonating. This combat strategy was meant to maximize damage against a single, powerful enemy.
With a loud explosion, the fireball detonated. The mutant zombie was blasted away, half of its head obliterated. It looked extremely gruesome. But even in this state, the mutant zombie wasn't dead and struggled to get up from the ground.
"Still not dead? Then let's do it again," Sylas said, forming another fireball. This time, he didn't charge it up but quickly released it. The mutant zombie was already severely injured, so a regular fireball should be enough to finish it off. Sylas was also concerned that if he took too long, the injured zombie might escape.
The fireball hit the mutant zombie's face, and upon explosion, it completely destroyed the zombie's head. This time, the mutant zombie was finally dead.
Sylas noticed a blue light emerging from the dead mutant zombie and being absorbed by him. The system interface showed a small increase in the energy bar for Fire Control, now at one-thousandth full. This indicated that he would need to kill a thousand more mutant zombies to level up the ability.
Sylas realized that only by killing mutant zombies could he enhance his ability's level.