Spirit Medicines are, as the name implies, medicines for one's spirit (Ki). They are the result of development of the medical science in the field of Inner Energy. The common trait of all known Spirit Medicines is that they can affect the Ki of an individual in order to bring the desired result for the body.
The Dan is translated into two different ways, depending on the case, Pill and Medicine. Since the Medicine is also used with the meaning of Pill, they are synonyms, thus use of either of the two is valid and does not change the meaning of Dan.
Spirit Medicines have been shown to be a rare category even within the Murim. However, they are widely used. Among them are common pills that are used for medical purposes. The most rare pills, which are usually the most extreme, are used to strengthen or increase someone's Ki, to give a boost in strength or even to control people.
Known Spirit MedicinesEdit
Il-Wol Sin-Dan (One Moon Divine Medicine)Edit
The greatest creation of the medical sciences in the whole Murim. There are said to be only three pills in the entire Murim and the cost for each one is one billion won (assumed currency). Upon ingestion the pills causes the body to create limitless amounts of Ki resulting in the break down of the individual's body and death. The only known way to control the pill's Ki creation is the use of advanced Ki distribution techniques such as the Black Heaven and Earth Technique. If the techniques are used and the Ki is stabilized in the body then the person immediately has the potential to become a Real Master because in order to hold the infinite amounts of Ki the use of the Black Heaven and Earth Technique causes the same change in the body as the fourth and final stage of training. It is also the only known confirmed cure of the Yin Body Types. This is probably because since the pill creates so much Ki the areas that are blocked from Ki distribution are forced opened and the formerly supressed Ki begins circulating.
Hwan Dan (Circulation Medicine)Edit
According to Shi-Ho it helps circulate the Ki of the individual who consumes it. It has never been seen used.
Ma-Hwan Dan (Evil-Circulation Medicine)Edit
Seung-Jae Bae was able to create a spirit medicine that maximizes the amount and quality of the Ki circulating around the body while it activates the circulation of Ki with an explosive effect enabling an individual to use martial arts even with a broken Ki-Center. However, the pill's function is temporary and it's explosive effect causes afflictive after-effects like excessive fatigue and an over-heating of the organs. The person who consumes them cannot stand up properly with exceptions being individuals of high stamina. There seem to have been various versions of the Ma-Hwan Dan:
- The first Ma-Hwan Dan was applicable only to people that already use Ki. 
- The S.U.C.'s initial Ma-Hwan Dan allowed Murim-ins and normal people alike to use high level techniques by activating their Ki. 
- Later on, S.U.C. started to use a Ma-Hwan Dan that not only enabled the use of martial arts for murim-ins and normal people alike, but also capable of controlling people's minds. People who ingest become confused and easily manipulated  resulting in them being brainwashed as well as showing more violent behaviour.
Jin-Gi Dan (Accelerating-Ki Medicine)Edit
The Jin-Gi Dan is the spirit medicine made by the Mil-Yang Clan and is an improved version of the spirit medicine, Ma-Hwan Dan, created by Seung-Jae Bae. Just like with the second version of Ma-Hwan Dan, by ingesting this pill an individual is capable of using martial arts even with a broken Ki-Center. The difference is that this accelerates the Ki and does not have the explosive effect of the Ma-Hwan Dan. The after-effects are seemingly non-existent and the effect of the pill lasts longer than its predecessor.
Bo-Hyul Dan (Blood Supplement Medicine)Edit
The Blood Supplement Pill, created by the One Moon School, as the name suggests, is a pill that speeds up the body's mechanism for the creation of blood by temporarily activating the Ki.
A form of sedative that enables someone to suppress memories that they wish to forget.  Although, it also seems to make someone more obedient towards certain individuals and their instructions which gives it a brainwashing effect. There is implication that this sedative relates to the Ma-Hwan Dan due to its effect on the individual's behaviour but nothing is yet confirmed.
- Shi-Woon Yi: Shi-Woon was given the Illwallsidan by Shi-Ho Lee. Due to ingesting and processing this pill Shi-Woon Yi's body is now a spirit medicine in and of itself after managing to control it with the assistance of Chun-Woo Han and the Black Heaven and Earth Technique. It has been hypothesized that anything but a fatal injury would be healed overnight.
- Jang So-Sul: Although hasn't eaten it herself, So-Sul has also witnessed the effects of the One Moon Divine Dan (Illwallshidan) through Shi-Woon's blood given to her in an effort to help her after she had a shock attack due to her condition. Until that moment she was unable to even talk a lot and was easily getting tired but after drinking some of Shi-Woon's blood her condition improved to the point that she could converse normally and her stamina had clearly increased.
- Shi-Woon Yi: He was given the pill by Seung-Jae Bae while he was looking along with Jang-Il Jeong for a way to get stronger when he was unable to use martial arts due to his broken Ki-Center.
- Chang-ho: He was given the Ma-Hwan Dan by the S.U.C. enabling him to use Ki-based martial arts at the cost of his own health.
- Soldiers Under Command: They used an enhanced version of the Initial Ma-Hwan Dan that literally activated the Ki in a person's body, enabling even normal people to use high-level techniques. They later, enhanced it further, giving it effects that allow them to control their follower's minds and construct their behavior as they wish. 
- Shi-Woon Yi: Shi-Woon is the only known user of both the Ma-Hwan Dan and Jin-Gi Dan. After he accepted the help of the Mil-Yang Clan he was given this pill after experimenting on the Ma-Hwan Dan. He used it later on to defeat Yong-Hyun Yan while protecting Jin-Ie Kwon and for his training after that because his Ki-center was broken during that period.
- Shi-Woon Yi: When Shi-Woon was caught by the S.U.C., through Seung-Jae Bae, and was almost made into a medicine, Sera Kang went to his rescue and gave him the Bo Hyul Dan to help him restore his lost blood. This makes him the only known case. Although, the effect of this Dan implies the possibility of its not-so-rare use for medical purposes.
- Chun-Woo Han: The pill was given to Chun-Woon by Sophia in order to help him forget his painful memories. Although the pill also made him more obidient to other people's intractions showing that it has the effect of brainwashing.  This effect made people believe that Chun-Woo was given the Ma-Hwan Dan  although a relation between the two medicines is possible.