For mortals, the most important things for survival have always been water and wood.
Usually, only large households have their own private wells, while common folks either go to the riverside to fetch water or use communal wells.
As for firewood, it is indispensable for daily cooking, boiling water, and heating during winter, thus it holds the top priority among the essential daily affairs.
Leng Yutang's proposal addresses the most pressing daily needs of mortals under current conditions.
"Hmm, using thunder and lightning for illumination is indeed quite interesting!" Yun Mo contemplated for a moment, nodding in agreement: "Although Demon Cultivators occasionally light candles, they're not ordinary lamp oil, which naturally makes them bright and comfortable.
Mortals don't have the capability to obtain extraordinary lamp oil, so by using thunderballs as raw material, at worst, I can gather some more as a backup."
