In the Potterverse the cure for a divided soul was real remorse, read repentance. Rowling got it mostly right. Read Psalm 54:1, 4. Note that along with Psalm 41:4 captures the same notion. I am remorseful, repentant, disgusted with my sin. But helpless to deal with it. The psalmist cries to God to save him by His name acknowledging that God is the sustainer of the psalmist's soul. In the climax of the Potter books Harry pleads with Voldemort to show remorse, repent.
There are two things that strike me from this. First, I am powerless to deal with my sin apart from God, which Christ reinforces with John 15:5. Second, I need to read what my kids are reading. Ready to point out the truth or the error that lies within those pages.