Lu Weiwen's success rate in building her Foundation was very high, and the main factor was actually her gold virtue spirit body.
Jin de's double spiritual roots, which were based on his spirit body and metal, were not inferior to a single spiritual root.
From what Lu Qing understood, many forces would use some supplementary medicine to nurture geniuses with single spiritual roots. However, they would not use the foundation building elixir. Instead, they would try to break through. One or two out of ten might fail and die, but those who succeeded, without using a foundation building pill, would have greater strength and potential after reaching foundation building.
Moreover, with such a high success rate, even though the consequences of failure were terrible, it was enough for those who were determined to pursue the path to try.
