Soul Sorcery

A Soul Sorcerer finds themselves with an inept power to harness the souls of the living.  Mostly considered the most unholy of magic, it steals the souls of other humanoid creatures to be used for various things.  While the souls stolen, they are on your person and kept away from the afterlife so sorely sought after.  Many dark cults attempt to force newborns to endure the rituals needed to create the vessel for such souls to be contained, but very few succeed, usually with grave consequences.    

Soul Stealer

At 1st level you know how to steal someone’s soul and add it to your own.

 As a reaction you can steal the soul of any humanoid or anything that resembles a humanoid (an ogre, a bearded devil etc.) within 60ft of you.  You have a maximum of souls equal to your proficiency bonus + your CHA modifier.  If you exceed your maximum number of souls, you must succeed a DC 15 CON save or take 2d6 + 1d6 per soul over your maximum,  the DC of the save also increases by 2 for each soul you go over your maximum.

You can use a soul you have taken in one of the following ways.  The soul is used unless otherwise noted:

Siphon vitality: You recover the CR of the creatures soul you stole + CHA modifier HP back (if you have maximum it adds temporary HP)

Final Question: You can ask one of the souls you have stolen a question that they must answer truthfully to the best of their ability.  They do not know about any events past their death.  The soul can understand you even if you do not share languages.

Soul Power: You send a soul with your spell, infusing the spell with the might of a soul. You can empower one of your spells by 1d6 +  1d6 per CR of the creature necrotic damage as a bonus action for one soul.

Spiritual Mimicry

At 6th level you take on the original form of the creatures whose soul you stole, you look exactly like them as they were in the state you absorbed them with the exception that your eyes will glow green. You have your proficiency modifier of uses for this ability and can end it early as a bonus action. This works extremely close to the Druids wild shape ability (pg 66 PHB) with the exceptions that you can only shape into the souls you have collected, and the Cr of the creature you can turn into is half of your sorcerer level.  This ability lasts indefinitely out of combat, in combat it lasts for rounds equal to your CHA modifier.  The creatures you transform into lose their lair actions and their legendary actions.  Once you use all of your rounds for a soul it is depleted. However if you did not use all of your rounds and ended it early, the previous rounds have been reset (still depletes a use of this ability) and you may use the same soul again.  

If the creature was a spell caster you only have half the spell slots the creature had.

Skills of The Dead

At 14th level you can spend one of the souls you have collected to gain proficiency in any skill the creature whose soul you stole had.  If the creature has proficiency in a skill you already have proficiency in your proficiency bonus doubles.  You can do this with only one soul per skill.

Soul Mastery

At 18th level you have become a master of soul magic. You no longer have a maximum amount of souls, when using soul mimicry the maximum CR of the creature can be equal to or lower than your level.  As well your mimicry lasts for your CHA + proficiency amount of rounds.