Then Hermione read this: "In order to psychically possess a victim, one must be able to abandon one’s own Body and return to it at will. In its natural state, the Soul is unable to do this, as abandonment of the Body by the Soul constitutes death. A Dark wizard may, however, seize advantage from the Split that occurs in the act of Murder and acquire deathlessness. The final chapter of this book describes the procedure and requirements."