Since being repeatedly strengthened by a massive amount of soul power, and further tempered by the blessing power accumulated over a thousand years from the Will of Hell, Sterl's body had broken through some kind of limit.
His terrifying vitality and bodily resilience allowed his strength to continually condense and accumulate, without any sign of ceasing. His powerful soul granted him an exceptional level of insight, allowing him to continuously gain new realizations. Each new understanding merged with his existing abilities, fueling ever more powerful destructive forces.
Now, Sterl was like an atom that kept splitting, with each split exponentially expanding his strength.
The powers created by these splits were then reintegrated within him, forming a shape akin to nuclear fusion.