Spirit Stones灵石
língshí
Crystallized qi used as both currency and battery in cultivation worlds.
Spirit stones solve two problems at once: cultivators need portable qi for training and array-powering, and stories need an economy. A typical system grades them (low, middle, high, top) with exchange rates that make a single high-grade stone a fortune, so auctions, mining rights, and sect treasuries become plot engines. Variants include spirit crystals, immortal jade, and primeval stones, but the mechanics rarely change.
The trope also quietly enforces class structure in these worlds: rogue cultivators grind for stones while great sects sit on qi-rich veins, a resource gap that many protagonists, most famously the pragmatic Han Li of A Record of a Mortal's Journey to Immortality, spend whole arcs scheming around.