Important because they allowed warriors to briefly project their qi from their bodies.
The five types of qi had main five traits. Fire qi burns, metal qi corrodes, earth qi strengthens, wood qi regenerates and water qi improves agility. The more advanced your cultivation, the more traits from your qi u can bring out. Teachers with the water attribute can use it to freeze their opponents.
Some qi types were more suitable in certain situations than others. For example, Fire and Metal qi are suited to offence, earth and wood qi defence, and water qi improves both. To go a deep deeper lets oberve water. ust as how it is versatile in reality, water qi is versatile in uses as well.
If two qi's mix, they can produce a secondary trait. For example, earth qi mixed with metal qi creates a reinfor
