hmm, because it's probably relevant, I'll copy something into here immediatly
The workings of accupuncture
Knowledge of the lay of the puncture points alongside a Meridian that form the astral body is just half the rent - they are the factor that directs the effect, but not the activation method - which is why the bit of accupuncture humans learned from the sparse contact with fingerlings in ancient history is mostly useless. To bring a system out of balance, or to return it to balance, more Chi needs to be added, and a needle is a useful conductor. Upon piercing a meridian, the user must pump amounts of their own Chi into the foreign system, which is what causes the imbalance. The greater the amount of Chi transfered in relation to the natural Chi of the target, the greater the effect. So while using 10 Mana might just cause a small numbness to a target that possesses 500+ Mana, the same target becomes so much more susceptible once it has used up a lot of Mana. The very same target, towards the end of combat, having exhausted a good amount of Mana on various spells and superpowers and whatnot, will suddenly find accupressure to be extremely dangerous. With only 200 Mana left, 10 Mana points in accupressure could easily paralyze the entire upper body. If a target has used up all Mana, even small amounts of Mana can throw the system that much into unbalance that it may very well kill that target on the spot. The duration of the effect varies mostly on the bodies ability to cope with the unbalance - that is to say, a mind roll. If the mind roll to resist the effect upon introductions is passed (as per standard game mechanics), there may be no effect at all. The effect then persists for a while depending on how much mana was introduced, and how much the initial mind roll failed. Enemies who are able to actually identify what is going on, and have a great enough controle over their body, could try to purge the foreign mana through sheer willpower - however the concentration needed to do that is enormous (decent DC, vulnerable while doing so), and if failed, could just end up purging your own mana. If the foreign mana is left alone to do it's thing, it's risky to use your own mana for spells and superpowers, as it will only further tip the scale towards the effect - the numbness that you previously barely noticed may start to spread, and paralyze you eventually. The foreign Mana is of course useless for the target - it's hard enough to use your own mana to cast spell, entirely foreign mana is incredibly hard to controle. Enemies with abilities that focus on draining enemy mana might be able to make use of this mana though.
An entirely different kind of effect is the Chi-leak, which exists in two variants:
The external Chi leak: An accupressure point is opened outwards, and is held open by the foreign Mana that was introduced into the target, letting Mana slowly escape - the victim will lose Mana overtime. Unlike effect-based accupressure, this does not create an imbalance, so it's not getting more effective the less Mana a target has, but in fact, is more effective on targets that have a lot of mana -imagine it like water pressure. If there is lot's of Mana in the body, it will flow out faster than if there is little, in other words, the mana lost every round is % based, the percentage that escapes depends on the foreign mana introduced (I am thinking something about 5% medium, less would make hardly a difference, more would seem OP). As above, the duration depends on the compared mind roll upon activation, and the whole can actively be closed, given that you notice what is going on and have a somewhat decent understanding of the matter.
the internal Chi leak: Chi does more than just act as fuel for fireblasts, it also directs pretty much all processes in your body, and sustains them. The Mana in your list is just the excess Mana that can be used freely, and while using it will exhaust you, it will not actually interfer with, say, your heartbeat. Thats why it's possible to cast stuff using HP instead - it draws from your essential Mana pool, thus could potentially kill you if you overdo it. The internal Chi-leak aims at the internal circuit (high DC, this shit is difficult), and once successful, redirects essential chi (HP) into the excess chi (mana) pool. That is to say, your HP will slowly turn into MP until the leak is fixed, slowly shutting your bodies essential functions down. This is a very serious wound, as directly controling your essential Mana pool is rather difficult. The DC to actively close the wound is much higher as with normal chi afflictions. Targets whith very low mind have a relatively high chance of not even noticing the effect - and more or less die of internal bleeding
((Ratios as shown here made up, @Elf feel free interpret sensible ratios on your own for the scale of the effect, but keep in mind the general small effect - big cause thought. Imagine an old fashioned scale. It doesn't take all that much to tip it. So try to keep in mind the current categories, 50+ Mana is a noticable debuff, even at full HP. The entire combat style is aimed at slowly wittling the target down, and accupuncture perfectly suited to be a weapon of attrition))