Underworld Ecosystem Level 4

[Underworld Ecosystem Level 4 (Special Skill): Establishes an Underworld Ecosystem exclusively for Underworld cities, nurturing special lifeforms capable of living in the Underworld. It uses a special upgrade method and cannot be upgraded with experience. To upgrade, a complete ecological system must form in one part of the Underworld, and the Underworld must slowly be integrated into the real world.]

[Note 1: Since the Underworld Ecosystem skill forcibly used experience to break through the rules and increase its level, the ecosystem's requirements have not yet been met. Therefore, its extraordinary effects have not been activated. The extraordinary effects will activate only after all the requirements needed to complete the upgrades from Level 2 to Level 3 and from Level 3 to Level 4 have been fulfilled.]

[Note 2: Since the Underworld Ecosystem skill's breakthrough is incomplete, the channel from Level 4 to Level 5 will be temporarily sealed. Even after the Level 4 upgrade requirements are completed, it will still be impossible to reach Level 5.]

[Explanation: Even if someone can temporarily break through the rules, rules are still rules. This cannot be done forever.]

Looking at the information before him, Liu Zhi knew that things would not be so simple. It seemed that this thing could not be used casually after all.

After thinking it over, Liu Zhi wrote down the situation here, summoned an undead unit, and had them deliver a message to Sandru to inform him of what was happening.

However, Liu Zhi never expected that, for the sake of simplicity, the unit he had summoned would be an ordinary force with little combat power. Their existence would not affect the battle, and even if they ultimately lacked a battle standard, it would not affect Liu Zhi's situation here.

But when this unit arrived, it brought Liu