Yōryoku

Yōryoku (妖力, "Dark/Evil Power") is the antithesis to reiryoku, a form of energy that finds its origins with the Amatsu-Mikaboshi itself.

Overview
The energies that consist of Yin and Yang exist solely in the form of reiryoku. It was the movement of those two forces that allowed the Mikaboshi's hold over the primordial world to be broken. The remnants of this power were said to be imbued into all of life. However, by the actions of the first Kami to come about, living beings were to be fueled by a positive living energy known as "spiritual energy" in opposition to the dark forces of "evil energy", suppressing the latter for all eternity. This power seems to only be used by those who are able to access the Mukai.

Manifestations
Yōryoku can manifest in various different ways. While it can be released as Yōatsu (妖圧, "Dark/Evil Pressure"), just as reiatsu can be, which carries with it the dark intent and will of its host, it has many different uses that only those who are fueled by Kagaseo's power, the users of Mukai in other words, can actually manipulate and control. However, there have been word that many sorcerer managed to find ways of controlling this dark force.


 * Kashaku (呵責, "Torture"): A special technique that allows Yōryoku to eat away at any and all willpower that is brought before it. It can manifest in many different ways, such as a weapon or object, and can also be imbued into the user's own attacks, transforming them into something dark and heinous. Attacks such as Seireitou Kawahiru's Muken and Hōkōryū are severely hindered and nearly rendered useless because they are used by one's will itself. Kurama explained that in the human world, "torture" itself is the act of breaking a convict's will, and that this technique is the literal expression of this goal. The stronger the user, the stronger an effect the Kashaku will have on its targets.
 * Possession: By making physical contact with an opponent, it is possible to use the Kashaku to break their will and take control of them to use as puppets.


 * Shōki (瘴気, "Bad Air"): Otherwise known as Miasma, it is a highly corrosive and poisonous smoke-like mist that can be used for offensive and defensive purposes. It can also eat away at a person's will while destroying their physical body little by little, at a rate dependent on the user. Similar to Kashaku, it can be imbued into one's attacks and is dependent on the level of the user's yōryoku.


 * Jyaryū (邪流, "Way/Method of Evil"): Unlike Kidō, which is fueled by reiryoku, these are spells that are fueled by yōryoku. It is possible to use certain Kidō spells that are instead powered by yōryoku. The result is that they become "darker" variations. Also unlike its spiritual antithesis, it does not have a set list of spells, as each user of yōryoku takes it upon themselves to create their own spells for various purposes. Kurama, however, does claim that there exists tomes of Jyaryū spells. It is akin to the concept of black magic.

Kurama Kawahiru can use this form of energy freely, his Zanpakutō itself being the only known one in existence that uses Yōryoku in lieu of normal spiritual power.