Soul Currency

Soul Vessel

A captured soul must have a container. This is known as an Unholy reliquary. The use of a powerful spell will remove the soul, death will also allow access to the soul for a short period.
The type of reliquary has its own cost, and ritual needed to perform it.

An Uncommon Reliquary needs a religeous artifact worth 1000GP and will take a dark practitioner 1-6 weeks to transform it. Each week of the process the practitioner must make a DC Hard religion check. The DC goes down by 1d6 for each successive week. It automatically succeeds on the 6th week. It can hold up to 5HD of souls.

A Rare Reliquary needs a religeous artifact worth 4000GP and will take a practitioner 2-10 weeks to trasnform it. Starting on the second week of the process the practitioner must make a DC Very Hard religion check. Going down 1d4 each week. It automatically succeeds on the 10th week. It can hold up to 10HD of souls.

A Very Rare Reliquary needs a religeous artifact worth 9000GP and will take a practitioner 5-20 weeks to trasnform it. Starting on the 5th week of the process the practitioner must make a DC Very Hard religion check. Going down 1 each week. It automatically succeeds on the 20th week. It can hold up to 15HD of souls.

A Legendary Reliquary needs a religeous artifact worth 16000GP and will take a practitioner 10-30 weeks to trasnform it. Starting on the 10th week of the process the practitioner must make a DC Impossible religion check. Going down 1 each week. It automatically succeeds on the 20th week. It can hold up to 20HD of souls.

Capturing Souls

For 1d6 rounds following death. The soul energy of any slain creature will leach from the body. If an unholy reliquary is positioned beside the body and the uncantation (unique to each reliquary) is uttered, the soul will transfer within. Each vessel can contain up to its limit, ie. a 5HD reliquary can contain 1 5HD soul or 5 1HD souls.

Soul Uses

You can expend soul energy within the reliquary. The souls cannot be split up, so a 3HD soul must be spent as a 3HD soul.
Spell Component
For spells that target another creatures life force, positive or negative, the soul will replace all spell components needed as long as the target's HD is within 2xHD of the soul being used.
For spells that do not target a creaturs life force, each HD of soul energy will replace 250GP of components.
Spell Enchancement
When casting a spell you can use soul energy to enhance the spell's efficasy. You can raise the DC of a spell by 0.5 for each HD of soul expended. Alternativly you can add the same amount to attempt to hit a creature with a spell.
Healing
You can drink soul energy like a healing potion. Doing so lets you roll the HD of the soul within up to the amount they would have had and add your CON modifier to i.
Crafting Magical Items
You can weave the energy of souls into weapons or items. If soul energy is used alongside the construction of an item it can embue into the material. The craftsman must have proficiency in crafting the item.

1-5HD = +1

6-10HD = +2

11-15HD = +3

16-20HD = +4