This was a weaker soul, likely just a low-rank Mature Level monster.
Rod had already tried, the souls of Mature Level monsters only added a few points of strength when put into the Justice Execution, while the souls of Ungraded monsters didn't increase it at all.
At least a stronger or even more powerful soul was needed for the growth in strength to be considerable.
That is to say, it required something above the Mature Level, like the Fierce Level.
Fierce Level meant that in the Black Fog, it had completed its metamorphosis, representing a great threat and extreme danger.
Such monsters were not allowed to exist within the Royal City. Once they appeared, they would be quickly eradicated.
Therefore, Rod could only search outside the Royal City.
He hoped to encounter one here.
The rising black dust enveloped him, and the dead monster quickly dissipated into nothing.
