In The Originals Season 4, Episode 13, titled "," the Mikaelson family is forced to make a devastating sacrifice to save Hope from the all-powerful entity known as The Hollow . To defeat the spirit, Vincent Griffith performs a ritual that divides The Hollow into four pieces, sealing one within each of the four immortal Mikaelson siblings: Klaus, Elijah, Rebekah, and Kol . The Core Conflict and Sacrifice
: To prevent The Hollow from ever reuniting and regaining its power, the four siblings must remain eternally separated. If they ever come near each other, the dark magic will begin to corrupt them and the surrounding environment. The Originals - Season 4Eps13
: Because The Hollow is bound by blood to Hope, it can only be contained by those related to her by blood who are also immortal. In The Originals Season 4, Episode 13, titled