Once he decided on the races that he wanted, Lex decided to revisit his worker rules. Mortal humans weren't too dangerous, but they could manufacture weapons. Mortal weapons - even guns and the like - weren't too effective against cultivators because to break their barriers and defensive techniques, the weapons themselves needed some kind of spiritual energy.
The problem was that Qi training cultivators barely had proper techniques, and Foundation realm cultivators had them, but they could be overwhelmed. That was only taking into consideration humans and their technologies.
Nymphs, even mortal ones, had some elemental powers based on the type of nymphs they were. For example, Dryads were tree nymphs and were generally well known. Or Naiads, the nymphs of fresh water. But then there were also nymphs of the mountains, the seas, caves, ash, darkness and so on. Depending on the type of nymph they were, even as mortals, they had some control over their respective elements.
