The Plague Kings stood at the edge of the Death Abyss, constantly adjusting the release of their Destruction Poison.
The reason for the adjustments was actually to dilute the poison. If it were released at its original concentration, even the Gold Level Undead that entered would have no escape from death.
Fang Jie certainly couldn't afford to use a large number of Gold Level Undead for experimentation, not at this stage where resources were scarce.
Thus, the Plague Kings could only continuously dilute the deadly poison, which wasn't as simple as merely weakening it. Various adjustments were needed to ensure that the poison's effects didn't change and that no deviations occurred.
Regrettably, the toxicity had to be reduced, allowing the Undead to survive for a period of time.
This time was used for the Undead to adapt and to mutate.
