Resource: a brief explanation of "Qi"
First of all a quick description regarding the terms Wuxai and Xinxia:
Wuxia literally means “martial heroes” and is a genre of Chinese fiction revolving around a fantasy world of martial art heroes - whereas a similar genre Xianxia is a mix of historical, fantasy and also mythical/supernatural genres heavily influenced by Taoism, Buddhism but also Chinese martial arts, folklore etc… elements – this latter one includes spirits, demons, gods…
And now about Qi:
As the term Qi or Chi is a reoccurring topic and major theme regarding the character Hou Xin I thought it might be fortunate to explain this overarching concept in Chinese Wuxia and Xianxia:
Aside from just normal martial art moves, there's such a thing called "inner flow" or "Qi" (sometimes also Chi).
Powerful moves consume "Qi" - those moves including attacks distributed with seemingly superhuman strength, "flying moves" or actions like "impossible jumps" or blocking hits and projectiles mid air without touching them… - and all other seemingly “superhuman” abilities (e.g. enhanced sensory perception).
When “magic” is used, it is indeed not magic but the powerful control and utilizing of Qi-power with the help of spells or talismans.
The amount of "Qi" a warrior has at his disposal is cultivated and enhanced over years – and some are more “prone” to handle it and have a stronger “natural cores” than others – meaning not everyone has the same “power” and it is not an endless source.
Natural skill and level of training determine how “strong” a Qi-warrior is and how much Qi-source one has to tap into.
Usually the Qi is “stored” within the certain Meridians of a human body (yeah, think acupuncture points)
Once “Qi" is drained like during a fight or by casting spells it regenerates over hours to days up to the maximum level.
Maybe think of it as magic energy pool or Mana in fantasy games.
Though once a warrior “over-strains” his Qi-cores meaning drains them beyond a certain level, or even tries to pull off spells or actions requiring Qi while his “core” is empty it can lead to health or even life-threatening injuries, damaging organs or even breaking meridian points, latter causing the person to lose a substantial amount of their “martial art” or power to cast spells.
“Qi” can be transferred from one person to another, if the “transferring person” is skilled in this kind of action and has a strong enough “core source”.
It also can be used to heal internal wounds or at least speed up the healing process during meditation.