The user has authority and duty in the Afterlife, a place where the souls of the all recently departed go. Exact conditions of the dead vary depending of the pantheon, but every soul arrives there, and while some may face punishment, others may be rewarded.
User is able to command the dead, and have powers related to life, and death, souls in general as well as power to bind and restrict (dead are expected to stay there after all). Some may have duties and powers related to Death and bringing the souls where they belong.
Hades/Pluto (Greco-Roman Mythology), Ruler of the Underworld.
Once the undisputed God-king of the Hollow world of Hueco Mundo, Baraggan Louisenbairn (Bleach) ruled by virtue of being one of its strongest inhabitants.
A Renegade Shinigami/Soul Reaper, Sōsuke Aizen (Bleach) became the ruler of of Hueco Mundo after dethroning and subjugating its previous ruler, Baraggan Louisenbairn.
As the strongest Hollow/Arrancar left alive after Aizen's defeat, Tier Harribel (Bleach) became the new ruler of Hueco Mundo by default.
Davy Jones (Pirates of the Caribbean) is capable of switching between the world of the living and the dead. He also had power over both the seas as well as Davy Jones' Locker, his own pocket dimension and a purgatory afterlife where he rules, keeps his disease enemies, and where those lost at sea or taken by the Kraken dwell in with their worst fears come to life.
Papa Legba (American Horror Story: Coven) is the ruler of the many Hells the coven encounters
La Muerte (The Book of Life), Ruler of the Land of the Remembered.
Xibalba (The Book of Life), Ruler of the Land of the Forgotten
Hades (Hercules), Lord of the Dead and Ruler of the Underworld
Ms. Slither (Grim Adventures of Billy and Mandy) is the oppressive ruler of the Detention Dimension, a hellish-realm where bad children are sent to detention for all of eternity.
Lucifer Morningstar (DC Comics/Vertigo Comics), former ruler of Hell
King Minos (Dante's Inferno), judge of the damned and duke of Limbo.
Jubileus, the Creator (Bayonetta), Goddess of Light, and the creator and ruler of Paradiso and the angels that inhabit it.