Soul Magic

The acquisition of this Feat reflects long study into the nature of the soul, the energy it provides, and its connection to the Weave of magic.  Through experimentation, you have gained the ability to use stored souls as fuel for your spellcasting, giving longevity to your capability both on and off the battlefield.  This is, however, an incredibly dark practice, as the act burns the soul out leaving only ephemeral ash and forever denying this being existence in the afterlife.  Divine beings may take notice and take great interest in those disrupting the natural flow of souls or denying them their currency.

Soul Magic gives the following benefits

Soul Point Currency. As you capture souls through your chosen method, roll 1 of the target's type of Hit Dice.  Record the soul and result of the roll on your receptacle as the number of Soul Points it now contains.

For example, an Ancient Silver Dragon has 25d20 HD.  You would roll 1d20 on capturing its soul and record its entry similar to the following: Ancient Silver Dragon-11 SP

Soul Receptacle Capacity.  All Soul Receptacles have a limitation.  The focus of a Soul Cage spell can contain 1 mortal soul of up to 20 points, but other containers may have the ability to contain multiple souls and therefore have a larger limit.  Any Soul Points rolled on an individual soul beyond a container's maximum when adding the final soul will be lost (rolling an 8 on a d8 when there are only 2 points left, will result in a soul with 2 points stored).

Soul Casting.  When casting a spell, someone with this feat can opt to us Soul Points to cast instead of expending a spell slot.  The necessary number of Soul Points is listed in the table below.  As the spell is being cast, the caster selects a number of souls with at least enough Soul Points for the required amount of the spell level.  These souls are used as a supplementary material component to the spell and then removed from the receptacle, burned by the casting of the spell.  If the total Soul Points of souls used as components would have any points left over, those points are lost.

Soul Exhaustion.  The act of mortals using soul magics that are normally the purview of extraplanar entities is taxing to the caster's own essence.  Each time this feature is utilized to supplement spell casting, the caster gains a level of Soul Exhaustion This condition acts similarly to the Exhausted condition, but affects a vital resource much more profound than mere physical exhaustion.  The very life essence that animates and gives drive to the living is being sapped away, and as a consequence is significantly more severe.

While you have the Soul Exhaustion condition, you experience the following effects.

Soul Exhaustion Levels. This condition is cumulative. Each time you receive it, you gain 1 Soul Exhaustion level. You die if your Soul Exhaustion level is 6.

d20Tests Affected. When you make a d20 Test, the roll is reduced by 2 times your Soul Exhaustion level.

Speed Reduced. Your Speed is reduced by a number of feet equal to 5 times your Exhaustion level.

Spell Casting Affected. While affected by Soul Exhaustion, spell casters must make a Concentration check with a DC equal to 8 + 2 times your Soul Exhaustion level as they cast any spell.  Failing the check means the spell is lost.

Removing Soul Exhaustion Levels. Soul Exhaustion is much deeper than physical Exhaustion and is therefore much more tenacious.  This condition requires the completion of a Long Rest every day for 1 full week.  For each of those days that you spend resting and doing nothing more than light activity, accrue 1 day toward removal.  After 7 days, remove 1 of your  Soul Exhaustion levels. When your Soul Exhaustion level reaches 0, the condition ends.  Greater Restoration is still effective in removing levels of Soul Exhaustion, but only when cast with a 7th level or higher spell slot.  It otherwise functions as Greater Restoration and removes 1 level per cast.