The Philosopher’s Stone.
Li Wei had certainly heard of its legendary reputation. As mentioned before, the ultimate goals of alchemy were the elixir of immortality and the Panacea, and their "prerequisite technology" was the creation of pure gold. That meant "turning stone into gold"—and the Philosopher’s Stone was the "stone" in that phrase.
Of course, the Philosopher’s Stone was not specifically meant for making gold. Its true function was to transform one substance into another—which, in Li Wei's opinion, was already impressive enough.
"This thing isn't for making gold, is it?"
Li Wei looked around, but saw nothing remotely golden or glittering. At his question, the Holy Maiden nodded.
"Of course not. If you expect to use it to make pure gold, you're dreaming. Using it to achieve immortality is impossible as well. Its purpose is conversion-more specifically, converting energy."
"Converting energy?"
"Exactly. Although this world is no longer what it once was, the energy that created it is everywhere. Sunlight, water, wind—these forces can all be absorbed by the Philosopher’s Stone and converted into power to drive the entire castle."
"Drive the entire castle?"
At that, a very bad thought suddenly arose deep in Li Wei's mind.
"Uh... Miss Holy Maiden, what exactly are you planning to...?"
"Those demon worshippers have always wanted to find my castle and the Philosopher’s Stone so they could use it to serve their master. I couldn't do anything before, but that doesn't mean I can't now."
As she spoke, the Holy Maiden stepped forward and approached the Philosopher’s Stone. Then Li Wei saw a smooth stone pedestal slowly rise from the floor. The Holy Maiden reached out and pressed her hand against its surface. At her touch, several streaks of golden light appeared on the pedestal, and the entire room flickered.
Then the