The objective of this part of the main quest is to acquire the high purity ingot of ether, that Doctor needs to counteract the Meshera virus, allowing you to kill the at the bottom of Rehmido. Killing the generator will accomplish this. However, you can also complete the objective by using incognito and interacting with the generator. While it doesn't actually talk, the translation implies you're able to pick up what you need without any trouble. The old humankind here are probably some of the guardians of the ether that were mentioned in the plot of the original Elona.