My sister is a narcissist. My mother always let her off the hook as a kid. Is this what created the Satanic monster that she is now?

anything is possible

When a parent learns that their child is a satanic monster, their options are few and always unhappy. Many will drive them out into the wilderness to join the unclean spirits which dwell there. Others will toss them from a cliff or drown them in a river. It is a rare parent who has the strength to use hooks to draw out the evil in their child, piercing their flesh with the hook's barbs and bleeding the devils from within them. If your mother let her off the hook before the process was complete, then she bears the responsibility for what your sister has come, and the threat which she represents to the tribe.

But all is not lost. The ritual may yet be completed. You and the other men of your tribe must fashion new hooks; sturdy ones made of wood and bone with barbs which will sink deep into her possessed flesh and lodge firmly there. She is no longer a child, and a single hook is unlikely to do the job, and so it will take several of you to hold her down as she lashes and screams on the ground, attempting to use her devilish magics to free herself and ensnare your spirits and your minds. Do not let her! Keep her on these hooks as the foulness bleeds out, while the elders of your tribe chant their secret words over her, calling upon the spirit of the girl within to fight against the unclean thing roiling within her veins. When the black blood spilling from her wounds turns to red, and only then, will you know that the ritual is working and that the monster within her has been defeated. Scatter ashes from the burned remains of donkey bones and miscarried children over the blackened blood to cleanse the soil, or else the devil might rise again in a new form and take possession of one of your tribe once more.

The hooks must also be destroyed, as they are now unclean. Do not fall to the temptation to use them on another disobedient child in the years to come, or else they might become tainted as well. It is the responsibility of the parent not just to let their child off the hook, but to craft a fresh hook themselves with their own hands.

If you do these things, your sister will be returned to you, whole and healthy, and ready to birth many fine children who will strengthen your tribe, and whom she will know to never let off the hook if it is necessary for her to pierce their flesh as well.