The soul represents the life force within a creature. It carries all the burdens and rewards of each and every act committed through life, and it carries all the knowledge one has learned in a lifetime, even after death. It is so powerful that when a deal is made with higher powers of the universe, such as a warlock patron or a deity, the soul carries its mark. The soul is like an inner skin one can never flay. Since the soul is so powerful and significant, there are always some creatures who want to manipulate it to their own advantage, or to use it as a currency, in order to gain more power.
A soul must be captured and stored properly, which is a process that requires serious preparation. A soul can only be captured after it leaves the body (generally upon death) and only unholy reliquaries decorated with precious gemstones and arcane marks or foul prayers can keep a soul imprisoned within.
Some spells, such as Mark of Soul Siphoning, Soul Binding, and Soul Imprisoning, were invented by the most ruthless and malicious spellcasters in history for the purposes of storing a soul in this way. There are also rumors about some weapons that can contain the souls of certain creatures they killed.
An unholy reliquary generally costs 1000 gold pieces to craft and it can store the souls of creatures whose HD is between 1-5. Since the soul represents the life force, and acquired experiences "feed" the soul, the souls of creatures with a higher HD are harder to store; therefore, preparing a reliquary for such a soul requires additional preparations.
The prices of unholy reliquaries that can store the souls of creatures whose HD is between 6-10 are 4000 gold pieces, 11-15 are 9000 gold pieces, and 16-20 are 16000 gold pieces. To capture the souls of creatures of higher HD, the unholy reliquaries should be crafted by the connoisseurs of the task and their prices are, naturally, even higher.
Once a soul is captured and stored within an unholy reliquary, it can be used in many ways. Here are a few examples:
- Spell Component: While casting a spell, you can choose to use souls instead of using the material components needed. Souls totaling 5 HD can be used as spell components of 5000 gold pieces.
- Spell Enhancer: While casting a spell, you can choose to destroy a soul to increase the DC of the spell. The DC increases by 1 for souls of 1-5 HD, by 2 for souls of 6-10 HD, by 3 for souls of 11-15 HD, and by 4 for souls of 16-20 HD.
- Regaining Hit Points: You can choose to drink a soul as if drinking a healing potion, destroying the soul, and consuming the life essence within. Once you do so, you regain hit points equal to 5 x the HD of the soul consumed.
- Crafting Magical Items: A blacksmith with the ability to craft magical items can use souls to imbue armor and weapons. A soul of 1-5 HD can transform a nonmagical weapon into a +1 weapon, 6-10 HD can transform a +1 weapon into a +2 weapon or a nonmagical armor into a +1 armor, 11-15 HD can transform a +2 weapon into a +3 weapon or a +1 armor into a +2 armor, and 16-20 HD can transform a +2 armor into a +3 armor. The used souls are destroyed at the end of the process.
- Selling The Soul: There are many individuals and organizations in search of others in the universe to fulfill personal vendettas, to settle old bets, or to do other things of that nature. The best way to capture someone is to capture their soul in a small precious gem box. In this case, the prices differ greatly, depending on the job, as well as the identities of the creatures involved.
Capturing and storing a soul is an evil act (even if the soul is evil itself) since any soul that meets this fate is deprived of an afterlife. Also, time is not spent in peace for a captured soul as it always tries to break free and its captivity causes it great pain. However, destroying a soul is one of the most evil, unholy, and corrupt acts imaginable. Upon destroying a soul, a creature ceases to exist in its entirety.